Classics in the History of Psychology

An internet resource developed by
Christopher D. Green
York University, Toronto, Ontario
ISSN 1492-3173

(Return to Classics index)



Definitions Oa - Oq

Posted December 2001

O (in logic). Symbol for the particular negative judgment -- Some men are not white. Cf. A. (J.M.B.)

Obedience and Disobedience [Lat. obediens, from obedire, to obey]: Ger. Gehorsam, Ungehorsam; Fr. obéissance, désobéissance; Ital. ubbidienza, disubbidienza. Obedience is personal submission in intention and action to an authority imposed upon the individual; disobedience is intentional refusal or omission of such submission. If the authority be to something internal, it is still recognized as quasi-external or not self-imposed: so Socrates' obedience to his Demon, and St. Paul's to his 'heavenly vision.'

Obedience is a recognized factor in the training and also in the development of the social nature of the child. In education the question has been as to how far obedience can be inculcated by the enforcement of commands. In social psychology obedience has been recognized as an important factor in what has been called social HEREDITY (q.v.); and Bain makes it a schoolmaster to morality -- the obedience to a 'word of command' standing for and anticipating the recognition of the moral law. (J.M.B.)

Object (-ive; general and philosophical) [Lat. ob, off, over against, + iacere, to throw, to lie; the equivalent of Gr. antikeimenon, usually translated oppositum]: Ger. Gegendstand, gegenständlich, Objekt, objektif; Fr. objet, objectif; Ital. obbietto, oggetto, obbiettivo. (1) That in which the mind's activity terminates; that towards which any mental operation is directed. But since the TERMINUS (q.v.) of intellect and of volition may be distinguished, this most general sense easily breaks up into two others. (2) That which is known, considered as giving truth and reality to the knowing process. (3) That which is the goal of impulse or choice -- aim, end, ultimate purpose. But since the problem of knowledge has been chiefly as to how the external world may be known (knowledge of states of consciousness being taken as a matter of course), (4) object is often used popularly to mean 'thing.' (5) Combining with the philosophical sense, it then is set over against mind and consciousness as the external, often the material, world. This tendency is strengthened by the use of the word SUBJECT (q.v.) to denote mind, and is one of the two chief meanings of the adjective objective. (6) That which is known may also be distinguished from that which is only erroneously assumed or accepted -- from that which we deceive ourselves into believing; hence object is used as equivalent to real. This sense is not common with the noun, but is most frequent with the adjective objective, which designates that which belongs really to any subject-matter as distinct from that which is imported or reflected into it through the prejudices, illusions, fallacies, or errors of the person observing or judging: opposed to that which is merely in the mind. It is (2) above made more specific. (7) Objective then comes to mean the intrinsically real, or self-subsistent, having validity in itself -- e.g. 'duty is objective.' (8) In later scholastic philosophy, object and objective are used exclusively to denote that which exists simply and only as material of mental operations. The use is continued in Descartes and is found in Berkeley, who expressly calls the existence of objects as perceived their objective existence. The history of the transformation of this earlier meaning to the later ones will be found under SUBJECT. Cf. the next topic. (J.D.)

Literature: EUCKEN, Gesch. d. philos. Terminol.; thirty pages of citations in EISLER, Wörterb. d. philos. Begriffe. (J.M.B.)

Object (mental or psychic): Ger. Objekt; Fr. objet; Ital. obbietto. Whatever consciousness in any way cognizes or, cognizing, feels any kind of interest in.

The flight of a bird, the immortality of the soul, the ultimate constitution of matter, a man's personal identity, a toothache, an algebraic equation, social reform, the moral ideal -- all these are objects if and so far as anybody attends to them. The definition indicates a distinction between objects of interest and objects of cognition. But in ultimate analysis it would seem that knowing never takes place without some interest in the object, and evidently we cannot be interested in anything without having some cognizance of it, however vague and rudimentary. Objects as such exist for us only so far as we attend to them. But when we attend there is always some need, craving, appetite, inclination, whim, or other form of conative tendency, which seeks satisfaction in the object attended to. Cf. OBJECTIVE (in psychology).

It will be noticed that we give the word 'object' the widest possible meaning. Our justification is that for this wide application no other word or form of expression can be conveniently substituted for it. Pikler (The Psychology of Belief in Objective Existence) uses the term obiectiva where we should speak of objects. But there is no need for introducing a Latin word where a common and familiar English term is available. There is, however, a tendency in some writers to limit the application of the term to material objects. But there is no sufficient ground for this restriction. If we use the term for any object of consciousness, whatever its nature may be, we can easily indicate when we wish to refer to 'material objects' by calling them material. In the same way we can speak of psychological objects, mathematical objects, ethical objects, and so on. Cf. OBJECT AND OBJECTIVE. For the self considered as object see SELF, and REFLECTION. (G.F.S., J.M.B.)

Object-blindness: Ger. Seelemblindheit; Fr. cécité psychique; Ital. cecità psichica (degli oggetti). See BLINDNESS (mental).

Object-lesson: Ger. Anschauungsunterricht; Fr. enseignement intuitif, leçons de choses; Ital. lezione obbiettiva. A class-room exercise upon a concrete object, such as an animal, plant, or mineral.

A course of such lessons was once thought essential to a good school; it is now generally recognized that object-lessons are much more effective when made an early or concrete stage of the regular instruction in the various studies. Cf. OBSERVATION, FORMAL STEPS, and METHOD.

Literature: CALKINS, Object-lessons. In Proceedings of the National (U.S.) Educational Association, as follows: SHELDON (1863), 93-102; WILBUR (1864), 189-209; GREENE (1865), 245-70; LOTHROP (1870), 49-64, 155, and (1872), 17; CALKINS, in various volumes since 1872. (C.DE.G.)

Object Self: see SELF.

Objection [Lat. obiectus, from ob + iacere, to throw]: Ger. (1) Einwendung (Einwand), (2) Vorwurf; Fr. objection; Ital. obiezione. Opposition taking the form of (1) dissent, which is opposition to a truth or proposition, or (2) disapproval, which is practical opposition. The opposing statement, or the ground of opposition, is called 'an objection.' (J.M.B.)

Objective (in psychology): Ger. Objektiv; Fr. objectif; Ital. obbiettivo. Sometimes used as synonymous with physical or material, but for psychological purposes it is better to define as follows: Whatever belongs to the nature of the object as cognized, in distinction from the processes of cognition, feeling, and willing. (G.F.S.- J.M.B.)

The term 'objective' especially indicates the controlling and determining function of the object in relation to subjective process. The object, whether characterized by reality feeling or by explicit belief, prescribes to subjective activity the conditions of its efficiency. Subjective interest seeks satisfaction. But the means by which satisfaction is to be attained can only be revealed by trial. Subjective activity is always a process of experimentation; the result of the experiment depends on the object. This holds good whether the satisfaction sought is practical or merely theoretical.

Practical success depends on adjustment to conditions independent of our wish or will. A cat attempting to escape from a cage may claw, bite, push, and pull, now in this direction and now in that. But whether it will escape, and if so, how, is predetermined by the structure of its prison. It can only experiment. A man constructing a piece of machinery for a given purpose must adjust himself to the nature of his material and its mechanical, physical, and chemical laws. All such activities involve an experimental attitude, and in the result of the experiment the nature of the object is revealed. You take a spade and try to dig. You may at will determine the amount and direction of effort put forth, but the result is beyond your direct control. You cannot by mere subjective selection determine whether the ground shall prove yielding or unyielding, or whether the spade shall break or not.

The outcome of previous activity yields knowledge of the object, which defines and determines subsequent activity. In so far as previous effort is found to fail, new adjustment follows. Unsuccessful lines of action are discontinued or modified, and successful lines maintained and repeated. In this way the development of cognition is one with the development of conation. As knowledge becomes more precise, complete, and differentiated, so activity becomes more precisely, completely, and distinctively adjusted to objective conditions. 'It is the essence of conation to seek its own satisfaction. But success is possible only in so far as it has acquired a definite and determinate character. The more blind a craving or impulse is, the more helpless it is. The new-born infant feels the craving of hunger, and manifests it by diffuse movements and by cries. Its craving is exceedingly indeterminate, inasmuch as it has no cognizance of the special object which would satisfy it or of the means of attaining this object. Hence the felt want cannot work out its own satisfaction. The mother or the nurse must do for it what it cannot do for itself. . . . On the other hand, as a vague craving takes more definite shape, the infant becomes more and more capable of fulfilling its own wants. Throughout this process the original conation is an essential factor. It tends to define itself, and the gradual acquisition of knowledge through experiment is but another expression for the process whereby the originally blind craving becomes more distinct and differentiated. To this growing differentiation and distinctness correspond more and more special and complex movements. Thus the vague craving becomes the relatively definite impulse to suck the breast. Soon the infant, which could not at first find the nipple, points to the bottle. Further development brings preference for this or that kind of food, the use of knife and fork, and the earning of money to buy nourishment' (Stout, Analytic Psychol., ii. 83 f., somewhat revised).

In principle, what has been said of practical activity applies also to theoretical activity. In practical activity, our interest requires in its gratification the production of some change in the object other than the mere transition from being less known to being more known. On the other hand, theoretical interest is satisfied by a mere increase of knowledge. None the less, it is an interest, just as much as hunger, or thirst, or love of money. And the conditions of its satisfaction are inherent in the nature of its object, and are revealed in the processes of mentally experimenting with the object. If I am curious about the colour and other characters of a bird which happens to catch my eye, I look hard at it, and possibly use a field-glass. But when I thus take the initiative, the result does not depend on me, but on the objective conditions. Perhaps the bird flies away before I can examine it. In that case my curiosity is balked. The end of my activity was merely to have that activity determined and defined by its object. But if the bird flies away, the objective control which I am seeking is denied. If it waits to be scrutinized, the result depends on it, not on me. I want to know whether its breast is black or blue or red. But it is the object itself which decides in favour of one of these alternatives to the exclusion of the others. It is the same with higher processes. I attempt to solve a geometrical problem, and on my own initiative take this or that step. But the result depends not on me, but on the condition of the problem, the nature of space, and so forth. Or I attempt to follow the transitions in Hegel's Logic; as Hegel very rightly says, all I have to do is simply to fix my attention on absolutely indeterminate being, with the view of finding it intelligible. It absolutely refuses to be intelligible unless I supplement it with other conceptions. Thus it grows and develops before my eye. But its growth and development arise from its own nature. I only give it an opportunity by setting my attention in a certain direction -- by experimenting with it in a certain way. Cf. EXPERIMENTATION, SELECTIVE THINKING, and TRUTH. (G.F.S.)

Objective Right: Ger. objektives Recht; Fr. droit objectif; Ital. diritto obbiettivo. The first stage in the dialectical evolution of morality is, according to Hegel, that of 'Abstract Right.' This stage is otherwise described as 'Objective Right,' in its opposition to the next stage, that of 'Morality' or 'Subjective Right.' See Hegel, Rechtsphilos., Introd., § 26 (Dyde's trans., 32-4). (J.S.)

Objectivism [for der. see OBJECT]: Ger. Objectivismus; Fr. objectivisme; Ital. oggettivismo. (1) The theory which attributes objective validity to at least some of our ideas, and thus regards the mind as capable of attaining real truth. Opposed to scepticism and to phenomenalism.

(2) The theory which tends to neglect the mental and spiritual in its theory of reality.

(3) The theory, in ethics, which conceives the aim of morality to be the attainment of an objective state (so Külpe, Introd. to Philos., §§ 14 and 30). Cf. SUBJECTIVISM. (J.D.)

'Objectivity' is applied both (1) to products or creations, and (2) to thinkers, artists, agents, &c., which illustrate objectivism in any of these meanings. (J.M.B.)

Objectivity: see OBJECTIVISM.

Obligation (in law) [Lat. obligare, to bind]: Ger. (1) Obligation, Schuldverpflichtung, (2) Schuldverschreibung; Fr. obligation; Ital. obbligazione. (1) A legal duty of one person to do something or abstain from doing something for the benefit of another.

It confers or implies a right to service. In strictness, it implies an actionable right, and thus excludes mere parental obligations (Pollock, Jurisprudence, chap. iv. 84).

(2) A writing expressing such a contractual duty, generally under seal.

'Obligatio est iuris vinculum quo necessitate adstringimur alicuius rei solvendae, secundum nostrae civitatis iura' (Inst. of Just., iii. 14, de obligationisbus). The constitution of the United States forbids any state to pass a law impairing the obligation of a contract. A charter of a private corporation is a contract within the meaning of this provision.

Literature: POTHIER, Obligations; SAVIGNY, Das Obligationenrecht. (S.E.B.)

Obligation (moral): Ger. (sittliche) Verpflichtung; Fr. obligation (morale); Ital. obbligazione (morale), obbligo. That which is binding or authoritative in the nature of morality. (J.S., J.M.B.)

The problem of moral obligation may be said to be the central and all-inclusive problem of ethics -- the science of the 'ought' as distinguished from the natural sciences or sciences of what 'is.' Thus Sidgwick says that both ethics and politics are 'distinguished from positive sciences by having as their special and primary object to determine what ought to be, and not to ascertain what merely is' (Meth. of Eth., 1), since 'the fundamental notion represented by the word "ought" or "right,"' which is contained expressly or by implication in all ethical judgments, is 'essentially different from all notions representing facts of physical or psychical experience' (ibid., 27). The notion of oughtness or obligatoriness is, on this view, 'ultimate and unanalysable,' unique, the fundamental category of moral judgment; and the function of ethics is to determine the content of obligation: what we ought to do, or what it is reasonable or right to do. The notion of obligation implies, further, a conflict between rational and non-rational motives. 'In fact, this possible conflict of motives seems to be connoted by the term "dictate" or "imperative"; which describes the relation of reason to mere inclinations or non-rational impulses by comparing it to the relation between the will of a superior and the wills of his subordinates' (ibid., 36).

As a specific ethical problem, or as an explicit statement of the ethical problem itself, however, the problem of moral obligation is one that has arisen in modern times. The question of the obligatoriness of certain forms of action is closely connected with that of the authoritativeness of the law which prescribes them. The explicit question, Why ought I to do this or that? arises with the separation of the action, in its formal principle, from the end, of the 'ought' from the 'good.' The Greek moralists asked: What is the good of this or that action? -- and so ultimately: What is the good? Preoccupied with the beauty and attractiveness of the good, and tending always more or less to a hedonistic interpretation of it, they were not so apt to raise the question of its obligatoriness or imperativeness: the authoritativeness of the good lay in its goodness. Modern moralists, on the other hand, have asked: What ought I to do, and why ought I to do it? What are the true laws of conduct, and what is the source of these laws and of their validity? 'For the ego-centric point of view is substituted the homocentric' (Fonsgriève, Essai sur le libre arbitre, 479); for the teleological point of view is substituted the formalistic and the juridical. Further, the homocentric point of view is also, primarily at least, the altruistic. The question is: Why ought I to regard the good of others as well as my own, and at the expense of my own? The problem of moral obligation passes into that of social and political obligation.

Kant's distinction between the categorical imperative or morality and all other imperatives, as merely hypothetical, is epoch-making, and may be regarded as the definitive formulation of the modern, as distinguished from the ancient, view of morality. Still, we cannot say, with Renouvier (Sci. de la Mor., 95), that this Kantian distinction amounts to 'a complete reversal of the ancient points of view of the human mind as to the essence of morality.' For the Greek moralists all imperatives are hypothetical, that is, means to ends, except one, the supreme end itself. It is only because modern moralists, on the contrary, have separated the problem of the ought from that of the good, because they have rested in the conception of the rightness of the actions or in that of their conformity to law, that they have regarded moral imperatives as categorical. Even for Kant the ultimate ground of the categorical character of the imperative of morality is found in the ultimateness of the moral end, in the character of the moral being as an end-in-himself; and the recognition of such an end by the Greek moralists makes the morality, which is the means of its attainment, categorically, and not merely hypothetically, imperative.

The intrinsic inseparableness of the problems of obligation and end, of oughtness and goodness, is suggested by the utilitarian, and often egoistic, solution of the modern problem of duty, as well as by the conception of duty which results from the ancient conception of good. At the same time, important differences in result from the difference in starting-point. When this is duty, we are generally offered a doctrine of sanctions, a more or less external interpretation of moral obligation; when this is the good, its obligatoriness is conceived as intrinsic, and is rather an implication than an explicit attribute of morality.

The problem of moral obligation receives two main or typical solutions, and both are found alike in ancient and in modern ethics. The first may be called the rationalistic, the second the hedonistic or utilitarian. Ultimately, it is the difference in the conception of the end or good that determines the difference in the interpretation of obligation. Not only so, but a hedonistic view of the end seems logically to negate obligation as an ultimate category. As Sidgwick says, ethical hedonism is incompatible with psychological hedonism; and hedonism is generally psychological. It seems unmeaning to say that I ought to seek happiness -- my own, at all events. Accordingly it is to Kant's anti-hedonism or extreme rationalism that we must trace the intensity of his insistence upon the categorical character of moral obligation, or conversely. It is chiefly to the prevailing hedonism of Greek ethics, on the other hand, that the comparative unimportance of its doctrine of obligation is to be traced. Yet even hedonism has its doctrine of obligation, and in Greek ethics we find rationalism as well as hedonism.

That the virtuous or excellent life, the life which attains the good, is a life 'according to right reason,' is the fundamental conviction not only of Aristotle, but of his predecessors, Socrates and Plato. It is a doctrine common to the Stoics and Epicureans, and finds its earliest philosophical expression in Heraclitus. As a conviction of the ordinary moral consciousness, it is rooted in the Greek regard for reason as the source of order, not merely in human life, but in the universe itself. The 'measure' which is the secret of reality and of beauty, as well as of virtue, is set by reason. All fair and noble activity is subject to the law of reason; the mark of a base and ignoble act is that it transgresses this law. The one has form, the form which reason alone can give; the other is without form, because it is devoid of reason. The fundamental and inclusive virtue is that temperance of moderation which consists of observance of the limit set by reason.

Heraclitus anticipates the Stoics in the explicit assertion of the obligatoriness, for man, of obedience to 'the divine law from which all human laws draw their sustenance,' the law of the common or universal reason, the true 'nature' of man, as of all things. In obedience to this divine law, as contrasted with the promptings of ungoverned appetite, he finds the secret of human happiness.

For Socrates, Plato, and Aristotle alike man is, in his true nature, a rational or reflective being, and his true or characteristic life is, therefore, the rational or reflective life, the life obedient to law, as contrasted with the lawless life of unrestrained animal appetite. For all three philosophers wisdom is, if not the sum, at any rate the presupposition, of virtue. And if Socrates tends to trace the obligatoriness of the rational life to its pleasantness, and to resolve all virtue into prudence, Plato and Aristotle regard it as in itself obligatory upon man as a rational being. The question, Why should I act rationally? is -- they would say -- a meaningless, because an irrational, question. For both Plato and Aristotle the completely rational life, the life of reason itself, is the life of thought or philosophy. The life of ordinary human activity has only a secondary or incomplete rationality: it should, or ought to, be a life according to reason. The highest form of this life is found in the state, which is the individual 'writ large.' From the psychological point of view, Plato regards the supreme virtue of righteousness (dikh) as consisting in the obedience of the spirited (qumoV) and appetitive (epiqumia) elements of human nature to the rule of reason (logoV). Righteousness, or complete virtue, consists in the doing of its own proper work by each part of the soul; and reason's work is not merely to rule, as that of impulse is to obey, but, as legislative, to determine the work of the other parts. The obligatoriness of the rational life is implicit in Aristotle's view of human good (eudaimonia). This consists in energeia yuchV, that is, in the actualization of the human ( = rational) life-principle or self. Such true self-realization takes various forms in the various rational or excellent human activities and habits, which are all found to be cases of the mean or rational amount.

It is in the ethics of the Stoics, and especially of the Roman Stoics, that the conception of obligation becomes most explicit. The Stoics not only define virtue as living conformably to nature (omologoumenwV th fusei xhn), but distinguish two degrees of such conformity: (1) kaqhkon, outward conformity of 'fitness'; (2) katorqwma, inward conformity or 'rightness.' For the cynic scorn for law as mere convention (nomoV) they substitute reverence for it as the expression of the divine order of the universe. The Roman Stoics develop this legalistic conception of life, and especially the idea of the universal validity of social obligation, of that law of nature and of nations which binds together all members of the human race as partakers in a common reason, and makes them citizens of a common state.

The judicial view of morality received a new expression in Christianity. The Jewish rabbis had elaborated a complicated and casuistical interpretation of the divine law. For the outward and mechanical conformity which such a method encouraged, Christianity substituted the inward conformity of will and disposition, demanding righteousness of motive and intention, and not merely of outward act. It also interpreted righteousness, after the manner of the Hebrew prophets, on its social as well as on its divine side, identifying the love of God with the love of man. In spite, however, of the characteristic inwardness of Christian morality, and of the exaggerated expression of this tendency in the 'antinomianism' of the early Christian centuries, there grew up in the middle ages an elaborate system of ecclesiastical jurisprudence, a new Christian casuistry. Along with this there came to prevail a double standard of virtue and duty, a distinction between ordinary and monastic virtue, between those things which are obligatory upon all (commands) and those things which are merely 'counsels of perfection.' The Reformation marks the revival of the principle of inwardness, of the essential unity and absolute obligatoriness of all virtue, and of the right of the individual conscience to determine for itself all questions of duty.

Modern ethics begins with the effort to discover an independent basis of moral obligation in the nature of things, in reason, divine or human, rather than in the will of God. Grotius defined 'natural right' (ius naturale) as 'the dictate of right reason, indicating that an act, from its agreement or disagreement with man's rational and social nature, is morally disgraceful or morally necessary.' Hobbes, while denying that man is by nature a social being, yet recognizes certain 'laws of nature,' and regards certain forms of conduct as indirectly, if not directly, rational. The early British rationalists -- Cudworth, More, Cumberland, and Clarke -- insist upon the essentially rational, and therefore natural, character of all duty as determined by the immutable and eternal relations of things. They reassert, against Hobbes, the essentially social nature of man and the ultimateness of social obligation. This ethical rationalism is developed by Butler, who finds the seat of authority in the rational principles of human nature, conscience, self-love, and rational benevolence. As a rational being, man is a law unto himself: he has the rule of right within, in the constitution of his own nature, in which the rational or reflective principles are clearly fitted to govern, and the impulsive or unreflective principles to obey. 'We are constituted so as to condemn falsehood, unprovoked violence, injustice, and to approve of benevolence to some preferably to others, abstracted from all consideration which conduct is likeliest to produce an overbalance of happiness or misery.' This doctrine of the intrinsic nature of moral distinctions and obligations is further developed by the later intuitionists, who maintain the absoluteness and ultimateness, because rationality, or moral principles, and insist upon the authority of conscience as the revealer of such principles.

This rationalistic view of moral obligation has provoked an opposite view, that of the hedonistic or utilitarian school. According to this view, the consciousness of moral obligation is the individual's sense of the compulsoriness of right conduct; the 'ought' is the echo of the 'must.' Its source is to be found, therefore, in the 'sanctions' of such conduct, or in the penalties attached to the violation of moral law. These sanctions are primarily, as in Paley's theory, theological. By later utilitarians they are conceived as the natural consequences of wrong-doing, and more particularly as its social and political consequences, the penalties with which public opinion, whether politically organized or not, visits the transgression of its laws. According to Paley, a man is said to be 'obliged' when he is 'urged by a violent motive resulting from the command of another.' This definition is virtually anticipated by Gay, in his Dissertation prefixed to Law's translation of King's Origin of Evil (1731): 'Obligation is the necessity of doing or omitting something in order to be happy. . . . Full and complete obligation, which will extend to all cases, can only be that arising from the authority of God.' To Paley's religious sanction Bentham adds three others, the physical, the political, and the moral or popular. The physical or natural sanction he regards as the basis to which all the others may be reduced. For Mill, as for his predecessors, obligation is synonymous with motivation. His answer to the question, What is the source of the obligation of utilitarian morality?' consists in an account of its sanctions. Earlier moralists have erred, he thinks, in limiting themselves to the external sanctions. Far more important than any of these is the internal or psychological sanction, the 'feeling of unity with our fellow men,' the sympathy which binds us to our fellows and constrains us to act for their interest, even at the sacrifice of our own. Mill thus discovers the obligation, in the sense of motivation, of altruistic conduct in an altruistic impulse which is irreducible to terms of egoism; while, in his insistence upon the intrinsic superiority of certain pleasures or satisfactions, and upon the right of the 'higher' feelings to control the 'lower,' he commits himself implicitly to a doctrine of obligation of the rationalistic type.

The evolutionary utilitarians seek to account for the feeling of obligation by tracing its genesis. According to Spencer, the political, religious, and social controls are only the pre-moral controls within which the strictly moral control evolves, and from which it gradually emancipates itself. The former account for the coercive element in obligation; the latter constitutes the authoritative element, and consists in the consciousness of the intrinsic evolutionary superiority of the more complex, representative, and later-evolved feelings as principles of conduct, to the simpler, presentative, and earlier evolved. With moral progress, the consciousness of obligation, in the former sense, tends to disappear, giving place to spontaneity. Of this evolutionary or naturalistic view of moral obligation an extreme statement will be found in Guyau's Esquisse d'une Morale sans Obligation, ni Sanction.

As against the hedonistic and utilitarian interpretation of obligation, the rationalistic view has been reasserted by modern idealists, first in Germany and later in England and America. For Kant, the founder of this idealistic movement, all morality is summed up in the word duty, and in a sense which negates pleasure and disregards consequences. Duty is a matter not of act, but of motive. The good or dutiful will is the will that is moved simply by reverence for law, or for its own rational nature. Such a will is autonomous, a law unto itself, because an end-in-itself. For Hegel this subjective or 'conscientious' attitude is only a stage between 'abstract right,' or external legality, and that 'ethicality' in which the individual recognizes his unity with his fellows, and sees in the ethical institutions -- the family, society, and the state -- the concrete and objective expression of the universal reason and the ultimate ground of individual obligation. The latter view has found expression in Green's Prolegomena to Ethics, Bradley's Ethical Studies, and more recent works in English which, while reducing all specific duties to the fundamental duty of self-realization, yet, by interpreting the true or ideal self as the social self to which the lower and false, or merely individual and selfish, self ought to be sacrificed, emphasize the social aspect of moral obligation. This has also been emphasized, from the psychological point of view, by Bain, Baldwin, and others. Cf. ETHICS, ETHICAL THEORIES, DUTY, LAW, and SANCTION.

Literature: GEORGES FULLIQUET Essai sur l'Obligation morale (1898); FRED BON, Über das Sollen u. das Gute (1898); J. MARK BALDWIN, Social and Eth. Interpret. (1898); works on Ethics generally; BIBLIOG. F, 2, j. (J.S.)

Obscurantism [Lat. obscurare, to darken]: Ger. Obscurantismus; Fr. obscurantisme; Ital. oscurantismo. Opposition to intellectual progress or enlightenment arising out of ignorance or fear of the effects which enlightenment will produce on traditional institutions and beliefs; the principles of those who practise such opposition. (A.T.O.)

Observation [Lat. observatio, from observare, to look up]: Ger. Beobachtung; Fr. observation; Ital. osservazione. Attentive experience; especially, an act of voluntarily attentive experience, usually with some, often with great, effort. Cf. the following topics.

More or less fixity in the object is requisite. Indeed, experience supposes that its object reacts upon us with some strength, much or little, so that it has a certain grade of reality or independence of our cognitive exertion. All reasoning whatever has observation as its most essential part. Whatever else there is in the act of reasoning is only preparatory to observation, like the manipulation of a physical experiment.

Much stress has been laid upon the distinction between 'sciences of observation' and 'sciences of experiment'; and undoubtedly there is a great contrast between the proceedings, let us say, of the anatomist and of the physiologist. Although the anatomist has to make many experiments (with stains, for example), yet the stress of his labour comes upon the act of observation; while the preparations for observation of the physiologist are far more elaborate, and the mere act of observation itself often very easy and coarse. The difference is, however, chiefly one of degree, and from a philosophical point of view is of quite secondary importance. (C.S.P., J.M.B.)

Observation (errors of): see ERRORS OF OBSERVATION.

Observation (mental): Ger. Selbst- (or innerliche) Beobachtung; Fr. observation de soi; Ital. osservazione (interna, also introspezione). (1) The deliberate examination of what is in one's own mind, with consciousness of the act itself; called 'self' or 'inner' OBSERVATION (q.v.). Cf. REFLECTION.

The term thus defined is useful to indicate reflection for purposes of examination, and not merely as designating the reflective state of mind in general. One observes when he reflects, but when he observes he reflects for a purpose. Observation is the means of INTROSPECTION (q.v.).

(2) A second use (which is not recommended) makes observation synonymous with mere awareness of the progress of experience.

Literature: JAMES, Princ. of Psychol., i. chap. vii; BRENTANO, Psychologie; LADD, Psychol., Descrip. and Explan., chaps. i, ii. (J.M.B.- G.F.S.)

Observation (method of, in education). The acquisition of knowledge by direct sense-perception.

At one time teachers were inclined to regard observation as a method complete in itself, programmes being supplied with courses of so-called object-lessons. Educators are now disposed to view observation as but one step or stage in a rational method. This is, at all events, the position of the Herbartians. See METHOD, and INTUITION (in education).

Literature: Index to Proceedings of the National (U.S.) Educational Association; N.A. CALKINS, Object Lessons. (C.DE.G.)

Observations (adjustment of): Ger. Beobachtungsrechnung; Fr. calcul des observations; Ital. ordinamento dei risultati d'osservazione (suggested -- E.M.). The department of experimental or scientific method concerned with the treatment of experimental results to determine their evidential value.

The method of procedure in adjusting the results of a series of observations depends upon the nature of the particular problem had in view. The number and distribution of cases, the ERRORS OF OBSERVATION (q.v.) of various sorts, the comparison of the results of one series with another, the elimination of accidental cases or of those vitiated by this condition or that -- these are some of the questions concerning which exact analysis is required. An illustration of such adjustment of observations is presented under VARIATION (statistical treatment of). In many cases the application of the theory of PROBABILITY (q.v.) is demanded. (J.M.B.)

Observer: see SUBJECT (of experiment).

Obsession [Lat. obsessio, a besieging]: Ger. Besessenheit; Fr. obsession; Ital. ossessione, fissazione. (1) The explanation of marked neurotic and abnormal mental symptoms in a patient as due to the persevering efforts of an evil spirit to gain mastery over him.

It differs from POSSESSION (q.v., as also DEMONOMANIA) in that it emphasizes the efforts of the demon from without, while in possession the demon is supposed actually to be resident in the body, and must accordingly be exorcized by appropriate agencies.

(2) The persistent and irresistible presence of an idea or emotion; in this sense equivalent to an IMPERATIVE IDEA (q.v.). (J.J.)

Obversion [Lat. obversio, a turning]. Hamilton (Lects. on Logic, xiv, and especially Appendix V. iii) states that CONVERSION (q.v., also for foreign equivalents) in logic is sometimes called obversion.

This is a surprising statement, which neither he nor his editors are able to support by citations. It is, therefore, no unlikely that Hamilton took it at second hand.

Bain (Logik, Pt. I. Bk. I. chap. iii. § 27) says: In affirming one thing, we must be prepared to deny the opposite: "the road is level," "it is not inclined," are not two facts, but the same fact from its other side. This process is called obversion.' Bain gives no reference. The regular scholastic name for the process he describes -- a name given by Abelard (Dialectica, 225) -- is infinitatio. This word is very common (see, for example, Albertus Magnus in II. Peri hermeneias, iii; Ockham, Logica, II. xii, xiii; and the index to Prantl, Logik, iv). But somebody may have got the notion that it was 'barbarous,' and have preferred to use a more classical-sounding designation. (C.S.P.)

Occam (or Ockham), William of; so called from Ockham, England. Studied at Merton College, Oxford; became a Franciscan, 1319, and then studied at Paris under Duns Scotus. He became the most eminent of Nominalists. He opposed the pretensions of the pope to political power and the possession of property. He was finally summoned to trial, and took refuge (1328) with Emperor Louis of Bavaria. He never signed the article of recantation, although he sought peace with the pope late in life. He died in 1347. See OCCAMISM.

Occamism: Ger. Occamismus; Fr. doctrine d'Occam; Ital. dottrina di Occam. The doctrine held by the followers of William of Occam, the founder of scholastic Nominalism (see REALISM). They were also called Terminists, because of the doctrine of Occam that universals are not anything really existing, but are only termini, predicables. (J.D.)

Occam's Razor: see PARSIMONY.

Occasion (-al): see OCCASIONALISM, and CAUSE.

Occasional Cause: see OCCASIONALISM.

Occasionalism [Lat. occasio, an event]: Ger. Occasionalismus, Theorie der Gelegenheitsursache (occasional cause); Fr. occasionalisme, hypothèse des causes occasionnelles; Ital. occasionalismo. The theory that matter and mind do not act upon each other directly, but that upon occasion of certain changes in one, God intervenes to bring about corresponding changes in the other. Each is then called the 'occasional cause' with reference to the other.

The theory was developed by Geulicx and Malebranche in order to deal with the problem -- arising from the extreme dualism asserted by Descartes between thought and extension -- of the interaction of mind and matter in general, and of the body and soul in particular, combined with the growing difficulties felt in forming any intelligible theory of causation. The same problem was dealt with in the single-substance theory of Spinoza and the Leibnitzian doctrine of pre-established harmony. Descartes in general had asserted that all changes of matter-in-motion are to be accounted for by reference to extension, while all psychical matters are to be referred to the nature of mind. This latter theory, however it might do for clear and adequate ideas, could not explain confused ideas and the passions and emotions connected with them. Here was an exception, and God had arranged in man a co-existence of the two substances, so that a disturbance of the 'animal spirits' (centering in the pineal gland) excited in the mind an unclear idea, whether sensation, passion, or emotion. This doctrine of influxus physicus was so obviously contradictory to the rest of the system, that the Cartesians at once set about doing away with it. With Geulincx the causal problem was the chief one; and he denies completely the possession of any efficient causality by matter. Its changes are, so to speak, only 'cues' upon which God effects the real results. Malebranche adds to this point of view the epistemological one: not only can one substance not directly influence the other, but they are so heterogeneous that mind cannot know matter. We 'see things in God,' matter again being the occasion rather than the real object of our knowledge.

Literature: DESCARTES, Principia, § 36; Meds., v and vi, Passions de l'Âme; GEULINCX, Ethics, 113; Met., 26; MALEBRANCHE, Recherche de la Vérité, vi. 2, 3; FALCKENBERG, WINDELBRAND, UEBERWEG, Histories of Philosophy (Index of each, sub verbo). (J.D.)

Occult [Lat. occultus, hidden]: Ger. verborgen; Fr. occulte; Ital. occulto. That which is hidden or secret. Cf. MAGIC.

It is applied to the assumption that insight into and control over nature is to be obtained by mysterious and magical procedures, and by a long apprenticeship in secret lore. The physical sciences of the middle ages, alchemy and astrology, and in modern times spiritualism, theosophy, and palmistry, contain various factors of occult lore. Such doctrines, known as Occultism, fall outside the realm of modern science. See MAGIC. (J.J.)

Literature: A. E. WAITE, The Occult Sciences (1891); JASTROW, Fact and Fable in Psychology; OTTOLENGHI, Suggestione e facoltà psichiche occulte (1900). (J.J.- E.M.)

Ockham: see OCCAM.

Ockham's (or Occam's) Razor: see PARSIMONY.


Oecology [Gr. oikoV, a house, + logoV, science, discourse: Ger. Oekologie; Fr. oecologie; Ital. ecologia. The science of economics as applying to plants and animals.

The term is principally used by Haeckel, oecology not being, at least yet, a clearly recognized branch of biology. (C.S.M.)

Offence (in law) [Fr. offense; Lat. offensa]: Ger. Verbrechen, Vergehen, Übertretung; Fr. crime, délit, contravention (Code Pénal, art. 1-5); Ital. delitto. (1) A transgression of law, which is punishable as a public wrong; a crime or misdemeanour.

(2) In English law, a petty crime, not the subject of an indictment, punishable by a pecuniary forfeiture.

A criminal prosecution for an offence does not exclude a civil action by the party injured for the damages he has sustained. In France the two remedies may be joined.

In early societies not directly affecting the state, wrongs to individuals seldom found a public prosecution. When private vengeance becomes unlawful, it is replaced by a civil action for damages, or for a fixed sum by way of legal compensation. See Holland, Jurisprudence, chap. xvi. 322. (S.E.B.)

Ohm: see UNITS OF MEASUREMENT (electrical).

Oken, Lorenz. (1779-1851.) Educated in natural science and medicine at Würzburg and Göttingen. Professor of medicine at Jena, 1807; of natural science, 1812; resigned for political reasons, 1819; professor in Munich, 1828; in Zürich, 1832; a pupil of Schelling.

Olfactometer: see LABORATORY AND APPARATUS, III, B, (e).

Olfactory Nerve: see NERVOUS SYSTEM, III.

Olfactory Sensations [Lat. olfacere, to smell]: Ger. Geruchsempfindungen; Fr. sensations olfactives, odorat; Ital. sensazioni olfattive. The sensations aroused by adequate stimulation of the olfactory mucous membrane in the nostrils, called those of smell. The stimulus is called odour.

The number of qualities is unknown, although attempts have been made (latterly with some success) to distinguish groups or classes of smells. Smell intensities probably obey Weber's law. The human organ is very readily fatigued, but its degree of exhaustion varies with different odours. Certain smell sensations are complementary or antagonistic. Olfactory sensations are difficult of revival in idea, but this sense has a very high associative and distractive value. (E.B.T.)

Literature: modern literature begins with TOURTUAL, 1827. ZWAARDEMAKER, Physiol. d. Geruchs (1895); ARONSOHN, Du bois-Reymond's Arch. (1886); v. VINTSCHGAU, Hermann's Handb. d. Physiol., III. ii. 225; VALENTIN, Lehrb. d. Physiol. d. Menschen, II. ii. (1848) 277; FRÖHLICH, Sitzber. d. Wien. Akad., math. -naturw. Cl., vi. (1851) 322; E. H. WEBER, Arch. f. Anat. u. Physiol. (1847), 342; J. MÜLLER, Handb. d. Physiol. d. Menschen, i. (1835) 759; SANFORD, Course in Exper. Psychol., expts. 57-60; PASSY, Année Psychol., ii. 362; art. Olfaction, in Dict. Encyc. des Sci. Méd. de Déchambre. (E.B.T.- L.M.)

Omnipotence [Lat. omnis, all, + potens, powerful]: Ger. Allmacht; Fr. omnipotence; Ital. onnipotenza. The attribute of God by virtue of which he is conceived to be able to realize all the possibilities presentable to his thought.

Omnipotence does not involve the ability to realize all possible conceptions, since there may be conceptions of the impossible or the self-contradictory. Nor does the omnipotence of God imply that all the conceivable possibilities are or will be realized. There may be alternative possibilities of which the choice of one will exclude the other. Nor does it imply that ethically God can contradict the moral attributes of his nature. The infinite holiness of God excludes the possibility of sin. That God should sin is not a contingency presentable to the divine thought.

Literature: see ATTRIBUTES (of God). (A.T.O.)

Omnipresence [Lat. omnis, all, + praesens, present]: Ger. Allgegenwart; Fr. omniprésence; Ital. onnipresenza. The attribute of God by virtue of which he is conceived to be present in the unitary wholeness of his being in every manifestation of reality.

God may be conceived as pantheistically present in every manifestation of reality; that is, as the substance of the manifestation itself. But he may also be conceived as present causally and effectually, or even in a negative and excluding sense. The nature of omnipresence is opposed to that of diffusion; God cannot be present in part. His presence in every part of the world must be whole and undivided.

Literature: see ATTRIBUTES (of God). (A.T.O.)

Omniscience [Lat. omnis, all, + scire, to know]: Ger. Allwissenheit; Fr. omniscience; Ital. onniscienza. The attribute of God by virtue of which his knowledge is conceived to be ideally complete and comprehensive of the whole nature of reality.

Assuming the existence of an intelligent deity, omniscience as an attribute of his nature cannot be denied. But supposing the question in debate to be that of the divine existence, then the most direct and cogent proof of the necessary existence of infinite and complete knowledge somewhere arises from the relativity and imperfection of human knowledge. St. Augustine develops this proof on the positive side, arguing from the existence of truth to the necessity of an infinite and absolute standard of truth; and recently Royce, in The Conception of God, develops the proof from the negative datum of the existence of error; also from the fragmentariness and incompleteness of human and finite knowledge. This necessitates the existence of an All-knower. Whether omniscience arises from the identity of God's thought with reality, or from its perfect correspondence with the real, is a debatable question in the metaphysics of religion. God's omniscience is a necessary presupposition of his fore-knowledge and fore-determination.

Literature: see ATTRIBUTES (of God); ST. AUGUSTINE, Contra Academicos; ROYCE, The Conception of God. (A.T.O.)

One (the) [AS. n, one; Gr. to en]: Ger. das Eine, Eins und Viele (one and many); Fr. l'un (et le multiple); Ital. l'uno (e il molteplice). A technical term of the Neo-Platonic philosophy denoting the absolute first principle -- a principle above both Being and Thought, since these are both subject to definition and (in so far) to limitation. For the less ontological senses of the term see UNITY.

In the later oral teachings of Plato, he seems to have been much influenced by the doctrines of the Pythagoreans, and to have attempted a synthesis of their theory of numbers with his own theory of ideas. In this doctrine he identified the One with the Good with the supreme Idea and Being (see Trendelenburg, Platonis de Ideis et Numeris Doctrina), and attempted to derive from it the series of other ideas. This tendency was carried still further in the Old Academy. Speusippus dsitinguished the One from the Good, the One being the principle of which the Good is the result; and also from reason, which is reduced to the plane of the Platonic World-soul, as moving cause (Zeller, Philos. d. Griechen, II. i. 851-3). In other words, the formal or logical cause was placed above both the final and the efficient. Xenocrates made the One and the Dyad the supreme ground of all existence -- the One being the first or male God, the Father and Nous; while the Dyad (indefinite plurality) is the mother; from their marriage arose numbers, and the Soul is Number which is self-moving. These fantastical distinctions found a fertile soil in neo-Pythagoreanism and Neo-Platonism, and it is in the latter that the One becomes the supreme category. With Plotinus, the Absolute is entirely ineffable and incomprehensible; and can be described only as simple relation of Being to itself, excluding all distinction and all relativity, to express which the term the One, or the Only One, is chosen. From this the whole hierarchy of subordinate beings and distinctions radiate or emanate, without either efficient or purposive activity upon its part. Jamblicus desired to make the One still more transcendent and ineffable, and accordingly distinguished between the First One and the Second One, which is interposed between it and plurality, and is the source of further emanations. Proclus carries the doctrine to its end by declaring that the Absolute, since undefinable and unknowable, cannot be called even the One except figuratively. From it, however, proceeds a plurality of Ones, which are simple and supersensuous, and through which emanation proceeds towards Being and towards Thought.

Literature: ZELLER, Philos. d. Griechen, III. ii. 491, 521, 688, 793, 846; PLOTINUS, Enneads, VI. ix. I. (J.D.)

One (the) and The Many: for foreign equivalents see ONE. See the ONE, and UNITY AND PLURALITY.

Oneirology [Gr. oneiroV, dream, + logoV, science]: Ger. Oneirologie; Fr. (1) onirologie, (2) oniromancie; Ital. onirologia. (1) The science of DREAMS (q.v.) and (2) of their interpretation.

Cf. SLEEP (also for literature). Oneiromancy is a better term for (2). (J.M.B.- G.F.S.)

Ontogenesis [forder. see ONTOGENY]: Ger. Ontogenesis; Fr. ontogenèse; Ital. ontogenesi. (1) The more restricted sphere of the ONTOGENY (q.v.) of particular organs or functions.

We speak of the ontogeny of a species, but of the ontogenesis of a specific or other character.

(2) Also used more widely for the problem of development as a whole as contrasted with the ontogeny of a particular species or group of the whole.

For the distinction between ontogenic and ontogenetic see GENETIC. (J.M.B., E.B.P.)

Ontogeny [Gr. wn, ontoV, a being, + genh, birth, development]: Ger. ontogenetische Entwicklung; Fr. ontogénie (more specialized than ontogenèse -- Y.D.); Ital. ontogenia. A term employed in biology and psychology for individual development as contrasted with racial evolution or PHYLOGENY (q.v.).

Since the publication of Darwin's Origin of Species there has been much discussion as to the relations which the facts of ontogeny and phylogeny bear to each other. Haeckel, to whom the introduction of the terms is due, strongly supported the principle of RECAPITULATION (q.v.), that in ontogeny we have a more or less complete though abbreviated recapitulation of the phylogenetic evolution of the species. Although many observers have criticized this principle in detail, and shown that the completeness of recapitulation is never perfect, and often very imperfect, still there is, by general consent, much in ontogeny which serves to throw light on phylogeny. Cope and Hyatt have contended that by acceleration or retardation in ontogeny the order of recapitulation may have been profoundly modified and a new basis afforded for phylogenetic changes. Mehnert, following Agassiz, has urged that the rudiments (Anlagen) of stronger functional organs may appear in ontogeny earlier than those of weaker organs which preceded them in phylogeny. Weismann's conception of germinal selection suggests a means by which the order of development in ontogeny may be changed and certain stages in recapitulation omitted. A further distinction is that between DEVELOPMENT (q.v.) and growth, both included in the conception of ontogeny. Cf. EMBRYOLOGY, and ACCELERATION. (C.LL.M.)

Hyatt has formulated the principle that the directions of decay in ontogeny -- in old age, &c. -- anticipate structural degeneration in the phylogeny of the species in the same directions -- a sort of reversed recapitulation (Science, Jan. 27, 1897), which with parallelism of the earlier stages in each series completes a parallel 'cycle' common to ontogeny and phylogeny (ibid., Jan. 29, 1897). (J.M.B.)

Literature: FRITZ, MÜLLER, Für Darwin (1863); E. HAECKEL, Gen. Morphol.; E. D. COPE, Origin of the Fittest; ERNST MEHNERT, Biomechanik erschlossen a. d. Principe d. Organogenese; AUG. WEISMANN, Germinal Selection; MORSELLI, Antropol. generale (1887-1900); (in psychology) BALDWIN, Ment. Devel. in the Child and the Race. (C.LL.M.)

Ontological Argument: Ger. ontologisches Argument; Fr. argument ontologique; Ital. argomento ontologico. The method of reasoning which infers the existence of God from a consideration of the content of the idea of God; ranked by Kant with the cosmological and physico-teleological as one of the three fundamental conceptions of rational theology. See RELIGION (philosophy of).

Its best representative is Descartes, who, however, unites the psychological method of St. Augustine with the purely logical one of Anselm. See SCHOLASTICISM, I.

St. Augustine, starting with the fact of doubt, infers then to the reality of the inner subject. This self-assurance involves certainty of being, of life, of feeling, and of rational perception. The certainty of being demands that reason be ruled by a principle which is its norm, which accordingly it does not itself generate, but which is above it. The idea of perfect truth thus involves the reality of perfect truth. See PATRISTIC PHILOSOPHY (6).

Anselm, on the other hand, works upon the basis of mediaeval REALISM (q.v.). The universals are the reals; and since there are grades and degrees of universality, there are all grades of reality. The most universal, God, is the most real -- ens realissimum. If one denies the existence of God, he must have the idea of God, and that means he has the idea of one than whom nothing greater can be thought. But to be in reality and in thought is greater than to be in intellect alone. Accordingly, if one have the thought of God at all, he must think of him as existing (Proslogium). This is often known as the 'Anselmian Argument.' Descartes argues from the existence of doubt to that of thought; and therefrom (by immediate inference) to that of the ego, and of mental processes and ideas as bare facts at least. Such facts much have a cause; the cause must be at least equal to its effect. One has ideas of perfection, and by this principle one cannot be the cause, because one is not perfect. Only a perfect being could effect such an idea. And, again, the very idea of God, or of the infinite, involves that of necessary existence -- his nature as such as to involve existence necessarily, not simply contingently, just as the idea of the triangle involves three-sidedness (Meditations, iii, and Principia, i. 14-6). In Spinoza the argument appears condensed into a definition of the Absolute -- that which can be conceived only as existing. Kant attempts to show that both the cosmological and the teleological depend upon the ontological, so that if this can be shaken, all rational theology is also shaken. It is a contradiction to think of God as non-existent, but it does not follow that God exists. Existence is not a part of the content of thought, but rather something which controls and necessitates thought -- something which is 'given.' Kant thus detects the essence of the whole rationalistic position in this argument -- viz. the assumption that thought as such is a valid criterion of reality; while in truth, according to Kant, thought, per se, is only analytic of itself, and requires sense-experience to get a judgment of reality. Hegel, throwing overboard the ontological argument as an argument from a thought, the particular thought of God, holds that fundamentally Thought as such determines Being -- or that at the root of all judgment is the presupposition of the identity of Thought and Being or God; and that the old ontological argument may be regarded as a vague anticipation of this underlying unity.

Literature: see under THEISM, and RELIGION (philosophy of). (J.D.)

Ontologism [Gr. ta onta, existing things, + logoV, science]: Ger. Ontologismus; Fr. ontologisme; Ital. ontologismo. (1) The philosophical (ontological) method which proceeds from logical categories directly to reality: it is applied to the great speculative systems of which the ontological postulates are not grounded in experience.

Hume and Kant vigorously opposed ontologism. For the newer developments of the method cf. Ueberweg-Heinze, Gesch. d. Philos., III. ii. (8th ed.) 328. (J.M.B.)

(2) The theory of the school founded by Gioberti in Italy (1801-52). The doctrine, namely, that the method and principles of philosophy should be sought for in the object, not in the subject.

The theory is a reaction from the supposed subjectivism of modern thought. Gioberti held that Descartes had substituted a psychologic method (see PSYCHOLOGISM) for the true ontological, and that modern philosophy, in so far as it proceeded from an examination either of consciousness or of the process of knowing, had put philosophy further off the right track, and had logically ended in sensualism, Protestantism, and atheism. We must begin with the supreme and objective intuition of the mind: Ens creat existentias. While the theory originally was in the interests of Catholicism, Gioberti himself gradually modified his philosophical views in a somewhat pantheistic sense, and politically became one of the chief apostles of an independent and united Italy. Ontologism was condemned by papal authority in 1861, and again in 1862 and 1866. Aside from Gioberti's political views, this result was probably inevitable, as his original system, in presupposing an adequate intuition of absolute being, tended to subordinate theology to philosophy, and, indeed, to make revealed religion unnecessary. Gioberti and his system are of interest to Americans through their influence upon O. A. Brownson. The latter, however, endeavoured to avoid the theological errors of Gioberti, and held that while his philosophy was ontological, he was not an 'ontologist' in the sense reprobated by the Church.

Literature: UEBERWEG, Hist. of Philos. (trans. by Morris, and appendix by Botta), ii. 497-509; LOUIS FERRI, L'Histoire de Philos. en Italie, i. 387; BROWNSON, Works, ii. 126, 468 ff. (art. Ontologism and Psychologism). (J.D.)

Ontology [Gr. on, ontoV, being, + logoV, science]: Ger. Ontologie; Fr. ontologie; Ital. ontologia. The doctrine or science of reality in its ultimate nature. Cf. METAPHYSICS, and PHILOSOPHY.

Plato uses the phrase ontwV onta to express the absolutely real character of the ideas; but being interested chiefly in the question of method in regard to them, uses Dialectic, not ontology, to denote the science which deals with them. Even Aristotle, who held that since every special science has its own peculiar sphere of existence (ousia, or on) as its object, there must be a supreme science which deals with existence in its generality, being as being, on h on, yet used the term 'first philosophy' or philosophy to designate this science. The Scholastics, while regarding Ens qua Ens as the object of philosophy, yet subdivided and named it on a different basis. It was accordingly Wolff who made the term current. Philosophy is first divided into theoretical and practical; the former, called metaphysics, is again divided into a general part (ontology) dealing with being in general, irrespective of whether it is material or spiritual; and a special part dealing with the three chief forms of being, namely God, the world, and the soul (see Erdmann, ii. 223-4, and Zeller, Gesch. d. deutsch. Philos., 183-8).

Wolff's identification of ontology with the logical principles of identity and contradiction had great influence (in a reactionary way) upon Kant. With Kant, ontology becomes a pretended science, since it attempts the impossible task of dealing with objects without any reference to the way in which they are given and known. Largely through his influence, ontology and ontological became terms of reproach, meaning vain attempts to deal with being apart from its presentation in consciousness (so G. H. Lewes and the English positivists generally). Sir William Hamilton defined it as the science which infers the properties of unknown being from its known manifestations -- or as Inferential Psychology! (Metaph., i. 124-5). The excess of emphasis upon the theory of knowing, as distinct from the theory of being, led, however, to scepticism and subjectivism, and so to a new conception of ontology as the science of the real, so far as that shall be determined through the process of knowledge: in other words, the question of the possibility of ontology is the question of the validity of knowledge.

Summing up, we may say that three stages are easily discernible. Ancient and even mediaeval philosophy are, as often said, predominatingly ontological; they are concerned with the objective, and it is assumed (naïvely or dogmatically) that being is as it is known to be, or that knowing is a process of participating in being, that it is itself a phase or factor in the structure of being. The second sense is the modern sceptical, or positivistic, in which it is assumed that being-in-itself (things as they really are) is to be sharply marked off from things in relation to us, or existence as presented through our senses, as phenomena. According to this view ontology is only the pretended and impossible theory of them. The third is the critical sense; the ancient dependence of knowing upon being is reversed; the first need is to examine the nature, possibility, and validity of knowledge, and then, through the results thus reached, go on to consider the being known. Thus ontology is no longer the general theory of being, distinct from its special forms; it is the theory of the known reality as distinct from the theory of the process of knowing. English thought probably owes to Ferrier (Inst. of Met., 47-9) the clear-cut recognition of this latter distinction of ontology and epistemology. (J.D.)

Ophelimity [Gr. wfelimoV]: Ger. Ophelimität (suggested -- K.G.); Fr. ophélimité; Ital. ofelimità. The power of satisfying an individual want; as distinct from the more general term utility, which sometimes means the power of satisfying a real need which it is advantageous to society to meet.

The double use of the term utility has produced a certain amount of confusion (Cairnes); and Pareto has suggested this new term to represent utility as each person judges it. It is possible that this term may come into more general use.

Literature: PARETO, Cours. d'Écon. Polit. (1896). (A.T.H.)

Ophthalmia [Gr. ofqalmia, a disease of the eyes]: Ger. Ophthalmie; Fr. ophthalmie; Ital. oftalmia. A term used to designate any form of inflammation of the conjunctiva. Many varieties are distinguished according to the character of the inflammation, its association with other diseases, &c. See Stephenson, Epidemic Ophthalmia (1897). (J.J.)

Ophthalmometry: see Eye, under VISION.

Ophthalmoscope: see LABORATORY AND APPARATUS, III, B, (1).

Opinion [Lat. opinio, used to translate Gr. dixa]: Ger. Meinung, Meinen (MEANING, q.v.); Fr. avis, opinion; Ital. opinione. Private and individual BELIEF (q.v.), whatever its grounds, recognized as private and individual. Cf. KNOWLEDGE (2).

The distinction between knowledge (episthmh) and opinion (doxa) played an important rôle in Greek philosophy. According to Plato, doxa mediates between knowledge and ignorance (cf. Eisler, Wörterb. d. philos. Begriffe, 'Meinung' and 'Erkenntniss,' for quotations from ancient and scholastic authors).

There is a tendency to make opinion a matter of tentative and somewhat superficial belief -- recognized as such by the subject himself (cf. Wundt, Logik, i. 370). However this may be, as to the holder of the opinion, the fact that it is individual, and also that it is not knowledge, gave it (the Stoics, Cicero) the suggestion of uncertainty and lack of objective ground, as in the expression 'mere opinion' (cf. Tarde, l'opinion et la foule, 1901). The distinction between belief and knowledge (cognition) now furnishes terms for the older antithesis. (J.M.B.)

Opinion (in philosophy). (1) Generally speaking, any idea or conception of fact, aiming at truth and regarded as probably approximating it, but confessedly not attaining certitude as regards it. It differs from HYPOTHESIS (q.v.) in not looking forward to future verification, nor aiming to serve any function of generalization or explanation. Its reference is rather to a condition of thought based upon evidence or inference not adequate to produce assured knowledge. It connotes belief, however, rather than doubt.

(2) Used in a more depreciatory sense to denote arbitrary or dogmatic preconception, e.g. a matter of mere opinion of unwarranted conviction.

The term now simply denotes a certain value or function of ideas taken in their objective reference; their worth as regards a standard of truth or certainty. As a technical term it is employed to translate the Greek doxa. Parmenides distinguished ta proV alhqeian from ta proV doxan. The former designated whatever had to do with reason, and apprehended truth and being; the latter designated mere custom and blind belief, and related to appearance, non-being, error. This sense of the term is connected with the Greek dokein, meaning both to believe or think, and to seem. This sense of mere seeming or appearance is taken up by Plato. Doxa refers to the region intermediate between being and non-being -- the realm of phenomena -- and is thus intermediate between mere sense (aisqhsiV) and rational thought (dianoia). It is subdivided into a higher form (pistiV, conviction; sometimes called right opinion, orqh, or alhqhV, doxa) and a lower (eikasia, conjecture, blind guessing). The former is based on reason (it is reasonable), though unaware of its basis -- not reasoned. It mediates the connection with discursive, or demonstrative, thought, and relates to those aspects of the sensible world that embody mathematical and teleological relations, which, however, cannot be stated per se (Theaetetus, 187-203; Timaeus, 270 ff.; and Republic, Bk. VI. 510). Aristotle to a considerable extent subdivides Plato's metaphysical conception into a logical and a rhetorical one. The former makes opinion a mode of judgment, hence arising in the soul as such, not from its affection by the body. As a mode of judgment, however, it does not rest upon an adequate syllogistic process, and hence does not reach demonstrative knowledge (Anal. Post., Bk. I. chap. xxxiii; Metaphysics, vii. 15). The point of connection with Plato is in the fact that Plato related opinion to the world of change, not of being. Now, whatever changes may be otherwise than as it is, and hence it is not necessary, but contingent. On the rhetorical side, doxa is a state of persuasion or belief, and the question of producing it is practical and psychological. Aristotle also makes much use of the conception of opinion in his ethics. All conduct relates to future, and therefore contingent, things -- matters of opinion. But it is of the highest importance that these opinions should be formed in accordance with will, rather than with merely desire. FronhsiV is the virtue of the habit of intellect in forming opinions in relation to right will. In general, doxastikon, the sphere of opinion, is the probable. Plotinus makes opinion the region intermediate between imagination and reason; all knowledge of the physical world as such is opinion. It depends upon the senses, but is found only in a soul which reflects and reasons.

After the distinction between the subjective and objective was clearly established, the nature of opinion ceased to be a metaphysical problem. It simply denoted one case of the more general principle -- the subjective. Consequently, in modern times, opinion hardly has a technical meaning. Hobbes uses it to denote the state of unstable and alternating ideas previous to judgment (Leviathan, Pt. I. chap. vii). Locke uses it in its present popular sense: the admission of something as true without assurance (Essay, iv. 15). Kant distinguishes matters of fact, of opinion, and of (rational) faith. The first refers to things, the existence of which can be proved either through pure reason or by exhibition in experience; the second refers to possible, but not actual, objects of experience in the world of sense, e.g. the existence of inhabitants of thought, but not of knowledge, i.e. God, immortality, the summum bonum (Critique of Judgment, Pt. II. § 91). (J.D.)

Opposition [Lat. opponere, to oppose]: Ger. Opposition (Streit Gegenwirkung); Fr. opposition; Ital. opposizione. Used as a general term to cover all forms of antagonism and interference, and made by Tarde one of three fundamental classes of phenomena recognized by science (Les Lois Sociales, 1898, Eng. trans., 1900; Opposition Universelle, 1896).

Cases of opposition are (see these terms) SUGGESTION (contrary), ANTITHESIS, CONTRAST, INHIBITION, CONTRADICTION, INTERFERENCE (in physics), ANTAGONISM (muscular), and, in technical sense, OPPOSITION (in logic), SOCIAL OPPOSITION, and CONSTRAINT (in social science). (J.M.B.)

Opposition (in logic). One of Aristotle's POSTPREDICAMENTS (q.v.). There are said, in the book of Categories (cap. x), to be four kinds of opposites. Relative opposites are relate and correlate of a disquiparent relation. Contrary opposites are the most unlike species of the same genus, as black and white, sickness and health. The third kind of opposition is between a habit and its privation, as sight and blindness. The fourth kind is between affirmation and negation. This passage has prevented the word opposite from taking any definite meaning in philosophy. (C.S.P.)

The following scheme is currently used to illustrate the forms of opposition as between the assertions of each two of the four propositions A, E, I, O (see those topics).


Optic Nerve: see NERVOUS SYSTEM, III.

Optical Axis: Ger. Augenaxe; Fr. axe de l'oeil; Ital. asse oculare. A straight line drawn through the centre of curvature of cornea and lens, and prolonged to the posterior wall of the eye. It is the sagittal axis mentioned under CENTRE OF ROTATION (q.v.).

Literature: HELMHOLTZ, Physiol. Optik (2nd ed.), 5, 88, 108; WALLER, Human Physiol., 412. (E.B.T.)

Optical Illusions: Ger. optische Täuschungen; Fr. illusions visuelles, illusions d'optique; Ital. illusioni visive (or ottiche). (1) Broadly, any visual perception or judgment which cannot be harmonized with the deliverances of the other senses or of vision under ordinary conditions. In this sense the term includes all physical illusions (effects of mirrors, lenses, prisms, &c.), the physiological illusions attending the perception of colour (after-images, contrast, colour-induction, &c.), and the physiological and psychical illusions attending the perception of space, movement, motion, and the character of objects. (2) In a more restricted and usual sense, it includes only the last group, and of these only those occurring with sound and sane observers.

I. Assimilative illusions. Illusions due to the assimilation of the sensory data with an improper group of ideas, i.e. illusions resting on a false interpretation of visual data, as the mistaking of a dimly seen stump for a highwayman by a timid traveller. Illusions affecting the meaning and character of objects belong to this class.

II. Equivocal figures. Mostly figures capable of two or more spatial interpretations. The double interpretation is most easy when the figures are observed monocularly. Fig. 1 (the figures are numbered consecutively on the accompanying Plates I-IV[1]) may be seen in the form of a partly open book with the back or the face towards the observer; Fig. 2 as a tetrahedron, erect or leaning backward. The first three of the group of forms marked Fig. 3 show similar possibilities with still simpler lines; all can be seen as right angles in perspective, and with two spatial arrangements of one or both lines. The fourth form is a reduplication of one of the simpler ones, intended to show their relation to Zöllner's Figure (Fig. 26). Two of the equivocal figures are known by special names: Fig. 5 is Schröder's Stair, and Fig. 6 Necker's Cube. Fig. 4 allows double interpretation of a non-spatial kind; the pattern may be regarded as black on a white ground, or vice versa. Inversions of relief may also be observed in actual objects when the ordinary criteria of relief are weakened or absent. Some investigators have classed these figures with the assimilative group; others have explained their behaviour by eye-movements and other perceptive factors.

III. Geometrical-optical illusions. These are false perceptions, or judgments, of the geometrical relations in plane figures, except such as involve irradiation, which are usually classed by themselves. Figures exhibiting the geometrical-optical illusions are numerous, as are also the theories for their explanation. In the absence of agreement among the latter no satisfactory classification is possible. The following may serve roughly, however, for purposes of description: (1) illusions of interrupted extent; (2) illusions depending on position in the visual field; (3) illusions of contrast; (4) illusions of contours; (5) perspective illusions; (6) special and miscellaneous figures.

1. Illusions of interrupted extent. In Fig. 7 the dotted space at the left is equal to the open space at the right, but seems larger; in Fig. 8, however, the single interruption reverses the illusion. Figs. 10, 11, and 12 are equal squares, but 10 seems too high and 11 and 12 too broad. Fig. 12 seems a little broader than 11, possibly because the central cross-line induces the eye to traverse the figure at that point, giving the interrupting lines their maximum effect.

2. Illusions depending on position in the field of vision. Vertical distances or extents in the upper part of the field are apt to seem too great. Fig. 14 is a perfect square, but seems a little too high; the lower parts of S's and 8's seem disproportionately large when inverted: S S S, 8 8 8. The illusion does not, however, appreciably affect the circle in Fig. 13. Figures lying in the periphery of the field appear distorted. Fig. 9, when drawn on a large scale and viewed with motionless eye at a distance proportional to the line below the figure, appears as a checkerboard of equal or nearly equal squares.

3. Illusions of contrast (Figs. 15 to 18). In Fig. 15 the central circles are equal, in Fig. 16 the central angles, in Fig. 17 the two parts of the line between the squares, in Fig. 18 the middle part of the lines, but in each case the circle, angle, or line seems smaller when adjacent to large extents and larger when adjacent to small.

4. Illusions of contour. In Fig. 19 the unclosed semicircle seems a little flatter and of a little greater radius than the closed; in Fig. 20 the parts of the interrupted cicumference seem a litte flattened as though belonging to one of slightly greater radius. In Fig. 21 the middle space and the open-sided squares on either side are equal and square, but the middle space seems a little too high and narrow and the open-sided squares a little too low and broad. These figures are examples of Müller-Lyer's 'illusions of confluxion.'

5. Perspective illusions. In Fig. 22 the perspective suggestion of the cube makes right angles seem oblique and oblique right. In Fig. 23 the converging lines, in proportion as they suggest perspective, influence the apparent height of the parallelograms. Variants of this figure in which human forms replace the parallelograms show the illusion more effectively. In Fig. 24 the addition of the oblique lines at the end of the lower pair of parallels makes them seem further apart than the sides of the little rectangle above. When these are not added the short parallels seem further apart than the long.

6. Special and miscellaneous figures. Under this head are grouped a number of figures which are usually known by special names, together with a number of other figures of more or less interest. Fig. 26 is Zöllner's Figure -- the presence of the short oblique lines distorts the actual parallelism of the long lines. Fig. 27 is Poggendorff's Figure -- the continuation of the left oblique line is really the lower of the obliques on the right, not the upper, as appears to be the case. Fig. 28 is Müller-Lyer's Figure, or the 'optical paradox' -- the central horizontals in the two figures are equal, but do not seem so. Of these three figures there are many variants. For example, Figs. 29 and 30, in which actual parallels are made to appear curved in opposite directions, may be regarded as variants of the Zöllner Figure; Fig. 32, in which the distance between the adjacent sides of the first and second circles is equal to the distance between the remote sides of the second and third, is a variant of the Müller-Lyer Figure; and Fig. 34, in which the right oblique if prolonged would cut the left oblique and the vertical in the same point, is a variant of the Poggendorff Figure, as in also the 'illusion of the Gothic arch,' frequently to be observed when a column is seen against a portion of an arch.

Besides these three figures there are a number of others that are sometimes referred to under the names of their originators, though the usage is not so well established. The illusion underlying Fig. 9 is known as Recklinghausen's Illusion; Fig. 15 is the Figure of Ebbinghaus; Fig. 17 is Baldwin's Figure; Fig. 23 is von Bezold's Figure; Fig. 25 is based on Loeb's Illusion; Fig. 29 is Hering's Figure (two or three other figures, variants of the Zöllner Figure, and Fig. 7 are sometimes also called by Hering's name); Fig. 30 is Wundt's Figure; Fig. 31 is Münsterberg's Figure (called also the Milton-Bradley Figure or the 'Shifted Checker-board Figure'); Fig. 33 is Mellinghoff's Figure; Fig. 34 is Delboeuf's Figure; Figs. 40 and 41 have both been called Láska's Figure. Pisco's Figure, not shown in the plate, is a variant of the Zöllner Figure.

Figs. 25, 31, 33, and 35-41 are miscellaneous figures that have played more or less of a rôle in the discussion of theories. In Fig. 25 the right one of the short parallels is a continuation of the single line above, but seems to be a little too far to the right; the long line at the left is supposed to lie in the median plane of the observer. Similarly, in Fig. 33 the three dots lie exactly in line with the short lines on either side of them, but seem a little too high. In Fig. 31 the central line is straight and parallel with the side lines. This figure has been regarded as a variant of the Zöllner Figure, but is really of a wholly different class, namely, of the irradiation figures. Fig. 35, showing the circle flattened at the corners of the square, was formerly regarded as an example of the 'over-estimation of small angles.' The two figures of Fig. 36 show the same effect, the horizontal line in the upper figure being bent downward very slightly at the ends, and in the lower figure bent upward. The principle of 'the over-estimation of small angles' has been found of limited application, and has been discarded as a principle of explanation. In Fig. 37 both trapezoids are of the same size, but the lower looks a little larger. In Fig. 38 the inner circle in the left figure and the outer in the right are exactly the same size; in Fig. 39 the two ring segments are equal, in Fig. 40 the two arms of the angle, but in no case does it seem so. In Fig. 41 the arms of the angle are equal, but that having the nearer dot usually seems a little longer.

Theories. The most systematic explanations are those of Lipps and Wundt. (1) Lipps sets up a principle of mechanical-aesthetic unity, in virtue of which every space form is endowed by us, in idea, with a living personality, or regarded as the scene of the interplay of mechanical forces. Our judgments of comparison are modified, unconsciously, by this anthropomorphic attitude. The circle, for example, is the result of the action of tangential and radial forces, in which the radial seems to triumph; the figure has therefore a centripetal character, which leads to underestimation: Fig. 13 looks smaller than 14, though the height and breadth of both is the same. (2) Wundt makes the illusion a matter not of deception of judgment, but of direct perception. It is conditioned by the laws of retinal image (fixation) and eye movement. Vertical distances, for example, seem greater than horizontal, because the expenditure of energy is greater in raising the eyes than in turning them through an equal angle to one side. These theories are typical of two great classes of theories: Lipps' theory of the judgment or higher process class, and Wundt's of the perceptive class. All the other proposed explanations may indeed be regarded as variants, or less perfect formulations of one or other of these. So we have the perspective theory of Hering, Guye, Thiéry; the contrast theory of Helmholtz, Heymans, Loeb; the contrast-confluxion theory of Müller-Lyer; the indistinct vision theory of Einthoven, &c.

The observation of the geometrical-optical illusions appears to begin with Oppel in 1854-5 (Jahrb. d. Frankfurter Ver.).

IV. Illusions affecting the perception of distance. Besides the geometrical-optical illusions there is an important group affecting the perception of the third dimension. Alteration of any of the ordinary criteria of distance or relief may open the way for illusions of this kind. They include the 'looming' of objects in a fog, the flattening of the dome of the sky, and the enlargement of the moon at the horizon, the alteration of relief with alteration of cross shadows, changes in inverted pictures or in the landscape when regarded with an inverted head, and many others. Here belong the illusions of the STEREOSCOPE, PSEUDOSCOPE, and TELESTEREOSCOPE (q.v.). See also ILLUSIONS OF MOTION AND MOVEMENT (visual).

Literature: optical illusions are treated in most of the standard physiologies, in many works on physics, and in the more recent textbooks of psychology. The following list has been confined for the most part to books and articles dealing exclusively with the matter in hand. For more extended references the general bibliography accompanying the 2nd ed. of HELMHOLTZ'S Physiol. Optik, and the annual lists of the Psychological Index, may be consulted. General: HOPPE, Psychologisch-physiologische Optik (Leipzig, 1881); SULLY, Illusions (N.Y., 1882); HELMHOLTZ, Physiol. Optik, 2. Aufl. (1896), especially §§ 28 and 30.

Equivocal figures: HOPPE, Beitrag zur Erklärung des Erhaben- und Vertieft-Sehens, Arch. f. d. ges. Physiol. (1887), xl. 523-32; JASTROW, The Mind's Eye, in Fact and Fable in Psychol. (1900); LANGE, Philos. Stud. (1888), iv. 405 ff.; LOEB, Arch. f. d. ges. Physiol. (1887), x1. 274-82; MACH, Beitr. z. Analyse d. Empfindungen (1886), 86 ff.; Sitzber. Akad. Wiss. Wien, math.-nat. Classe (1866), liv. 2. Abth., 393-408; ibid. (1868), 1viii. 2. Abth., 731-6; OPPEL, Ueber ein Anaglyptoskop, Pogg. Ann. (1856), xcix. 466-0; THIÉRY, work cited below under Geometrical Illusions. The original notice of Necker's Cube will be found in the Philos. Mag., Ser. 3, i. (July-December, 1832) 336-7, also Pogg. Ann. (1833), xxvii. 502-4; and of Schröder's Stair-figure, in Pogg. Ann. (1858), cv. 298-311. A number of the equivocal figures will also be found in SANFORD, Course in Exper. Psychol. (Boston, 1898), 254-60.

Geometrical-optical illusions -- general and theoretical: EINTHOVEN, Arch. f. d. ges. Physiol. (1898), 1xxi. 1-43; FILEHNE, Die geometrisch-optischen Täuschungen als Nachwirkungen, &c., Zeitsch. f. Psychol. (1898), xvii. 15-64; HELMHOLTZ, op. cit.; HERING, Hermann's Handb. d. Physiol., 3. Th., i. 370 ff., 536 ff., 552 ff., 564-84; Beitr. z. Physiol. (Leipzig, 1861-4), 65 ff.; LIPPS, in Helmholtz-Festgruss (Hamburg and Leipzig, 1891), 219-307 (abstract by the author, Zeitsch. f. Psychol., iii. 1892, 219-21); Raumästhetik und geometrisch-optische Täuschungen (Leipzig, 1897), vii. 424; articles in recent volumes of the Zeitsch. f. Psychol.; THIÉRY, Philos. Stud., (1895) xi. 307-70, 603-20, (1896) xii. 67-126; WITASEK, Zeitsch. f. Psychol. (1898), xix. 81-174; WUNDT, Abhandl. d. k. sächs. Gesell. d. Wiss., math.-phys. Cl. (1898), xxiv. 53-178.

On smaller groups or special figures: BALDWIN, The Effect of Size-contrast upon Judgments of Position in the Retinal Field, Psychol. Rev. (1895), ii. 244-59; see also Science, N.S. (1896), iv. 794-6; VAN BIERVLIET, Nouvelles Mesures des Illusions visuelles chez les Adultes et les Enfants, Rev. Philos. (1896), xli. 169-81; BINET, La Mesure des Illusions visuelles chez les Enfants, Rev. Philos. (1895), x1.11-25; BRUNOT, Les Illusions d'Optique, Rev. Scient. (1893), 1ii. 210-12; BURMESTER, Beitrag zur experimentellen Bestimmung geometrisch-optischer Täuschungen, Zeitsch. f. Psychol. (1896), xii. 355-94; DELBOEUF, Bull. de l'Acad. Roy. de Belgique (1865), 2e sér., xix. No. 2, 195-216, and ibid. (1865), xx. No. 6, 70-97; also Une nouvelle Illusion d'Optique, Rev. Scient. (1893), li. 237-41; CHRISTINE LADD FRANKLIN, A Method for the Experimental Determination of the Horopter, Amer. J. of Psychol. (1887-8), i. 99-111; see also Science (1896), N.S., iii. 274; GUYE, l'Illusion d'Optique dans la Figure de Zöllner, Rev. Scient. (1893), li. 593-4; HEYMANS, Quantitative Untersuchungen über das 'optische Paradoxon,' Zeitsch. f. Psychol. (1895-6), ix. 221-55; Quantitative Untersuchungen über die Zöllnersche und die Loebsche Täuschung, ibid. (1897), xiv. 101-39; HÖFLER, Krümmungskontrast, Zeitsch. f. Psychol. (1896), x. 99-108; JASTROW, A Study of Zöllner's Figure and other related Illusions, Amer. J. of Psychol. (1891-2), iv. 381-98; see also abstract in Nature (1892), xlvi. 590-2, and Rev. Scient. (1892), 1. 689-92; JUDD, A Study of Geometrical Illusions, Psychol. Rev. (1899), vi. 241-61; KNOX and WATANABE, On the Quantitative Determination of an Optical Illusion, Amer. J. of Psychol. (1893-5), vi. 413-21, 509-14; KUNDT, Untersuchungen über Augenmass und optische Täuschungen, Pogg. Ann. (1863), cxx. 118-58; LÁSKA, Du Bois-Reymond's Arch. (1890), 326-8; LOEB, Ueber Kontrasterscheinungen, Zeitsch. f. Psychol. (1898), xvi. 298-9; and Arch. f. d. ges. Physiol. (1895), 1x. 509-18; MÜLLER-LYER, Optische Urtheilstäuschungen, Du Bois-Reymond's Arch. (1889), Suppl. -Bd., 263-70; Zeitsch. f. Psychol. (1895), ix. 1-16; and ibid. (1896), x. 421-31; MÜNSTERBERG, Die verschobene Schachbrettfigur, Zeitsch. f. Psychol. (1897), xv. 182-8; OPPEL, Jahrb. d. Frankfurter Ver., 1854-5, 37-47; 1856-7, 47-55; 1860-1, 26-37; PIERCE, The Illusions of the Kindergarten Patterns, Psychol. Rev. (1898), v. 233-53; Science (1898), viii. 814-29; ZÖLLNER, Ueber eine neue Art von Pseudoskopie, Pogg. Ann. (1860), cx. 500-23, and ibid. (1861), cxiv. 587-91. A considerable collection of these illusions will be found in Bradley's Pseudoptics (a collection of simple apparatus, arranged by MÜNSTERBERG), and in SANFORD'S Course in Exper. Psychol., 212-54.

On the apparent form of the sky and size of sun and moon: BOURDON, Les Objets paraissent-ils se rapetisser en s'élevant au-dessus de l'Horizon? Année Psychol. (1898), 55-64; FILEHNE, Die Form des Himmelgewölbes, Arch. f. d. ges. Physiol. (1894), lix. 279-308 (contains a brief historical account of the older literature of the question); O. ZOTH, ibid. (1899), lxxviii. 363-401; see also two discussions of the subject, one in the Rev. Philos., nov. 1888 to fév. 1889, and the other in the Interméd. des Biol. (1898), 351-2 and 391-5.

On illusions of distance and relief (monocular): BREWSTER, On the Conversion of Relief by Inverted Vision, Philos. Mag., Jan.-June, 1847, Ser. 3, xxx. 432-7 (contained also in his work on the stereoscope); EINTHOVEN, On the Production of Shadow and Perspective Effects by Difference of Colour, Brain (1893), xvi. Pt. LXI and LXII. 191-202; MARGARET F. WASHBURN, The Perception of Distance in the Inverted Landscape, Mind (1894), N.S., iii. 438-40; see also some of the papers given in the literature on equivocal figures.

On illusions of motion and movement: AUBERT, Die Bewegungsempfindung, Arch. f. d. ges. Physiol., (1886) xxxix. 347-70, (1887) x1. 459-80, 623; BOURDON, Sur les Movements apparents des Points lumineux, Interméd. des Biol. (1898), i. 382-4; BOWDITCH and HALL, Optical Illusions of Motion, J. of Physiol. (1880-2), iii. 297-307; FISCHER, Stroboskopische Erscheinungen, Philos. Stud. (1886), iii. 128-56; HOPPE, Die Schein-Bewegungen (Würzburg, 1879), pp. xii, 212; MAYERHAUSEN, Studies on Chromatokinopsias, Arch. of Ophthal. (1885), xiv. 81-90; SZILI, Zur Erklärung der Flatternden Herzen,' Du Bois-Reymond's Arch. (1891), 157-63; 'Flatternde Herzen,' Zeitsch. f. Psychol. (1891-2), iii. 359-87. Cf. also GERTZ, and Skand. Arch. f. Physiol. (1899), x. 53-73, and STEWART, Amer. J. of Psychol. (1900), xi. 240-3. See also under ILLUSIONS OF MOTION AND MOVEMENT. (E.C.S.- H.C.W.)

Optics [Gr. ta optika, things pertaining to vision]: Ger. Optik; Fr. optique; Ital. ottica. (1) Psychological: the science of sight or vision.

This science includes (1) the anatomical description, gross and fine, of the total visual apparatus; (2) the dioptrics of the eye; (3) an account of the physiological functioning of the visual apparatus; (4) the doctrine of the visual sensation, and (5) that of visual perception. See the various subordinate titles, and also VISION. (E.B.T.)

(2) Physical: the science of light.

It includes the phenomena of reflection, refraction, diffraction, interference, absorption, &c., of light. See Light under VISION. (C.F.H.)

(3) Pathological: the science of abnormal and defective VISION (q.v., defects of). (J.M.B.)

Literature: general works on psychological optics are: HELMHOLTZ, Physiol. Optik (1st ed., 1867; 2nd ed., 1885-96); AUBERT, Grundz. d. physiol. Optik (1876); FICK, KÜHNE, and HERING, in Hermann's Handb. d. Physiol., ii. 1 (1879); VON KRIES, Die Gesichtsempfindungen und ihre Analyse, Du Bois-Reymond's Arch. (1882); and later papers in the Zeitsch. f. Psychol., &c.; G. E. MÜLLER, Zur Psychophysik d. Gesichtsempfindungen (1897); HERING, Zur Lehre vom Lichtsinne (1878), and later papers in Arch. f. Ophthal., &c. A full bibliography, up to 1894, is given by KÖNIG in HELMHOLTZ, Physiol. Optik (2nd ed.), 1017 ff., and after 1893 in the annual Psychological Index; see the literature of VISION, and cf. also BIBLIOG. G, 2, u. (E.B.T.)

Optimism and Pessimism [Lat. optimus, best, superlative of bonus, good, and pessimus, worst, superlative of malus, bad]: Ger. Optimismus and Pessimismus; Fr. optimisme and pessimisme; Ital. ottimismo and pessimismo. These are opposite correlative terms applied to the valuation of experience, life, and the world. Optimism is the view that the world is thoroughly good; or, that it is the best possible world. Pessimism is the view that the world is thoroughly bad; or, that it is the worst possible world. The problem is that of the relation of the world as a physical, or metaphysical, existence to its interpretation in ethical terms.

Plato, in the Timaeus, was the first to formulate the conception of optimism. His problem is the relation of the world as created to the demiurge, its architect. He made it, although sensible and changeable, after the pattern of the eternal and ideal; 'he desired that all things should be good, and nothing bad, so far as this was attainable,' and so the world, being like the fairest and most perfect of intelligible beings, is a 'blessed god' (34), and a 'sensible god, the greatest and best, the fairest, the most perfect possible, the image of its maker' (92). None the less, as created, as sensible, the world implies non-being, and hence evil. There is a limit set; the world is to be good, 'so far as that is attainable.' And in other of his writings he dwells in a somewhat gloomy spirit upon the evils thrust into the life of man by his connection with the sensible world and the material body, so that the good is reached by withdrawal from the created world (so in Phaedo, Phaedrus, parts of Gorgias, and the tenth book of the Republic). In this conception of the element of non-being in the world of experience, limiting the eternal good, Plato is the logical father of pessimism as well as of optimism. In him the Greek spirit was so strong that upon the whole the sensuous is looked upon as the plastic embodiment of the ideal, and hence as fair and good. But the elements are in unstable equilibrium, and it needs only to have the emphasis fall upon the negative limit to have a pessimistic result. The Stoics and Neo-Platonists continued the optimistic tradition of Plato, and so did the great Scholastics, following, however, in mode of statement, the Aristotelian teleology, rather than the Platonic tradition. The Epicurean and Sceptical schools were empirical rather than philosophical pessimists: they dwelt upon the actual bulk of pain and evil in the world, as confutation of the Stoic ethics.

Leibnitz repeats, in amplified form, a teleological optimism in his Théodicée. The world must be the best of all possible worlds, for it is the work of God. God through his wisdom knew all possibilities, and through his goodness chose the best of these possibilities, and through his power created it. Evil is of three forms: metaphysical, the expression of the necessary finitude of the world; physical, which serves to teach us law by punishing its infractions; and moral, which is a necessary phase of freedom. This optimism made its way through Wolff and others into the popular philosophy of the rationalistic enlightenment, and is seen, for example, in Pope. Like the optimism of the Stoics, it was met on empirical rather than philosophic grounds; notably by Voltaire's Candide, which, in its ironical treatment of Leibnitz, comes perilously near the doctrine that life is not worth living. In his Phil. ignor. Voltaire catalogues all the sources of woe in the world. Kant, in his early period, repeats the optimism of Leibnitz (Versuch einiger Betrachtungen über den Optimismus, 1759). In his critical period Kant holds that there is a radical evil in man's nature in his tendency to make self-love -- the particularistic, sensuous principle -- the motive of his actions. The good principle is that of humanity, which is rational and universal.

Rousseau had already raised the question of good and evil in the historic and social life of man, in his assertion that the primitive, natural man was thoroughly good, and was rendered throughly evil by institutions and culture. Kant took up this problem, in connection with his notion of the twofold structure of man just referred to; he held that in the state of nature the natural propensities are good, since adapted to their end. Physically there is 'Paradise,' morally a state of complete innocence. But man becomes conscious of himself, has a will, departs from the natural law implanted in his instincts, and evil arises -- the 'Fall.' Conscious desires lead to work, to the arts, to property, to civil relations, to culture. Through culture man's life ceases to be something produced by nature, and is self-produced. The conflict of nature and culture produces unhappiness, but is an ethical necessity incident to the recognition of rational law. The end of history is not the happiness of the individual, but the perfection of the whole of humanity. Conflict and suffering lead towards the latter. In short, Kant is a pessimist regarding man in his natural actuality, an optimist regarding him in his moral possibility.

Hegel seizes upon the three factors implied in the history now resumed: (1) the relation of the negative factor in creation to the Creator (where he utilizes Fichte's idea), (2) the relation of the particular and universal in man, and (3) the function of conflict and suffering in history; and attempts to make a synthesis of pessimism and optimism. Since the absolute is not a static fact or content, but a process, it involves negation, particularization, and consequent conflict and suffering within itself. But this conflict through differentiation is the dynamic of progress, and so functions for good. In a static cross-section the world is evil; in its movement (which Hegel calls 'actuality') it is good.

The French Revolution introduced the positive side of the negative teaching of Rousseau. It held that a reform of economic and political conditions was all that was necessary to initiate a tendency towards the infinite perfectibility of man. Malthus's doctrine of population was purposely intended to refute this conception. As generalized and applied by Darwin, it has carried over the question of optimism and pessimism into the biological sphere. One school points to the universality of the struggle of existence as teaching the lesson of pessimism; another, the contribution made by this struggle to development as indicating an optimistic conclusion. Spencer has used the evolutionary conception to argue to the self-destructive, and hence transitional, character of evil.

Schopenhauer is the pessimistic pendant of Hegel's optimism. Will, not thought, or reason, is the absolute -- the true thing-in-itself. This will is irrational, hence objectless; there is no progress or development, but only the restless play of purposeless will. Hence the will is essentially unhappy. Since the objective world is only a picture of this will, it must be a world of suffering. This metaphysical reasoning is reinforced by psychological considerations; desire is essentially painful, and its satisfaction, pleasure, is only the removal of pain. Hence pain must preponderate in life. All experience and observation confirm this result. Von Hartmann attempts what he regards as a synthesis of Hegel and Schopenhauer. There is a logical factor and an alogical one, both attributes of the unconscious. While the will-factor makes it better that the world should not exist than exist, yet the world is the best of all possible worlds, and continually evolving to higher intensities of consciousness. Its teleology is optimistic, although from the standpoint of satisfaction the world is evil.

Current popular thought phrases the problem in the question of whether life is worth living. Interest has shifted from the theological problem to the question of intrinsic value of life. Cf. MELIORISM. (J.D.)

Literature: besides the works cited, see much of the literature of ETHICS, and of the IMMORTALITY of the soul. Also SULLY, Pessimism; JAMES, Is Life worth Living? in The Will to Believe; LUBBOCK, The Pleasures of Life; and consult BIBLIOG. F, 2, k. (J.M.B.)

Optotype: see TEST-TYPE.

Opzoomer, Cornelius Willem. (1821-92.) Educated in Leyden. He became professor of philosophy at Utrecht. He was an empiricist of the positive type.

[1] Many of these, like geometrical figures generally, are common property. The original designers have never hindered their free reproduction. In exact form many of the figures given in the plates follow Sanford, and are reproduced with the consent of Messrs. Heath & Co., Boston.