DICTIONARY OF
PHILOSOPHY AND PSYCHOLOGY

Integral [Lat. integer, whole]: Ger. (1) ganz, (2) ergänzend; Fr. intégral; Ital. integrale. (1) Made up of parts in some way -- primarily spacially -- distinct: as in the phrase 'an integral whole.'

(2) Belonging, as one of distinct parts, to a whole: as in the phrase 'an integral part.' Cf. INTEGRATION (different topics).

The phrase 'in some way distinct' leaves open the question of the separateness of the parts when taken out of relation to the whole. Distinct means here more than distinguishable, and in most cases -- though possibly not always -- it means separable also, an integral whole meaning a whole of integrated parts. (J.M.B.)

Integral (in mathematics): see CALCULUS.

Integration (and Disintegration) [Lat. integer, complete]: Ger. Verknüpfung; Fr. intégration (suggested); Ital. integrazione. Integration is the act or process of bringing together as parts of a whole, disintegration the act or process of separation into component parts.

According to Herbert Spencer and his school, the integration ('aggregation,' 'concentration,' 'consolidation') of matter is one of the two most general momenta of the evolution process, and disintegration of the process of dissolution: 'Evolution, under its simplest and most general aspect, is the integration of matter and concomitant dissipation of motion; while dissolution is the absorption of motion and concomitant disintegration of matter.' (First Princ., § 97).

These transformations are undergone not only by every aggregate, but also by its more or less separate parts, and are exemplified also by the combinations of the parts. The local integration of like units is segregation. Directly or indirectly, integration and disintegration characterize the development not only of physical and biological phenomena, but also of psychical and social phenomena (First Princ., §§ 107-15; Princ. of Psychol., §§ 58-76, 380-3; Princ. of Sociol., §§ 224-7, 448-53, 763-7). They hold, moreover, of the totality of things; for 'the entire process of things, as displayed in the aggregate of the visible universe, is analogous to the entire process of things as displayed in the smallest aggregates' (First Princ., § 183). Cf. INTEGRATION (in psychology). (A.C.A.Jr.)

Integration (in mathematics). The method of the integral CALCULUS (q.v.). (J.M.B.)

Integration (in psychology). (1) A mental combination in which the composing elements remain qualitatively distinguishable.

Used loosely for combination, association (see REDINTEGRATION), &c., until given this technical sense by Baldwin (Elements of Psychol., 1893, Glossary). The suggestion of the term 'colligation,' as a translation of Verknüpfung (see Külpe, Grundriss d. Psychol., 21, 285; Eng. trans., 1895, 21, 277), is directly in the face of this earlier use of integration, besides having been used (Ger. Colligation) in a different sense by earlier writers. See COLLIGATION; cf. COMBINATION, COMPLICATION, and FUSION. It also has analogy with the more general use of the term and with its mathematical use. (G.F.S.- J.M.B.)

(2) The combination of qualitatively different contents of presentation in the apprehension of a single object (cf. Stout, Manual of Psychol.). This is a special case of meaning (1); and as another term, COLLIGATION (q.v.), has been used in this sense (as opposed to the union of disparate elements of all sorts), the first meaning is preferred.

(3) Spencer's use carried over into psychology. See the preceding topic. (J.M.B., G.F.S.)

Intellect (or Intelligence) [Lat. intelligere, to understand]: Ger. Verstand; Fr. intellect (intelligence); Ital. intelletto (intelligenza). The faculty or capacity of knowing; intellection or, better, COGNITION (q.v.) denotes the process. The corresponding adjective is intellectual (together with intellective, adjective of intellection). (G.F.S.- J.M.B.)

The earlier English psychologists used the word understanding rather than intellect. Locke's great work was entitled Essay on the Human Understanding. The corresponding title in Reid is Essay on the Intellectual Powers; but even he makes little use of the word intellect. In general, intellect is used in some kind of antithesis to sensation. But the contrast takes different forms in different writers. In Locke it is the contrast between sensations as material on the one hand, and the mind's elaboration of this material on the other. In Cudworth and similar writers the antithesis is between higher and lower faculties of knowing, and assumes a Platonic form. 'There is a superior power of intellection and knowledge of a different nature from sense which is not terminated in mere seeming and appearance only, but in the truth and reality of things, whose objects are the eternal and immutable essences and natures of things and their unchangeable relations to one another' (Selby Bigge, Brit. Moralists, § 831).

There is a tendency to apply the term intellect more especially to the capacity for conceptual thinking. This does not hold in the same degree of the connected word intelligence. We speak freely of 'animal intelligence'; but the phrase 'animal intellect is unusual. However, the restriction of the term to 'conceptual process' is by no means so fixed and definite as to justify us in including it in the definition.

As 'intellect' stands for the capacity, intellection stands for the process of knowing. Here again there is a tendency to restrict the term to conceptual thinking. Ward does so definitely and consistently. Croom-Robertson, on the other hand, gives the word the widest possible application, making it cover all forms of cognitive process. On the whole, if the term is to be employed at all, Robertson's usage appears preferable, as corresponding better to the generality of the words intellect and intelligence. See also CLASSIFICATION (of the mental functions). (G.F.S., J.M.B.)

Literature: see the textbooks of psychology; BIBLIOG. G, 1, c, 2, p; EISLER, Wörterb. d. philos. Begriffe. 'Intellect' (especially for scholastic distinctions under Intellectus).

Intellection: see INTELLECT.

Intellectualism: Ger. Intellectualismus; Fr. intellectualisme; Ital. intellectualismo. (1) In psychology: the theory which finds the intellectual or cognitive function more fundamental than the affective and conative, and accounts for the other functions in terms of it.

Applied especially to Herbart's doctrine of the 'mechanics of presentations,' of which feeling and will are functions.

(2) In philosophy: the theory which (a) makes the ultimate principle of the universe some form of thought or reason, or (b) holds that reality is completely intelligible to thought. Cf. IDEALISM (1).

It is opposed to VOLUNTARISM (q.v.) and to what might be called affectionism, which make will and feeling respectively the ultimate explaining principles. In this meaning it is especially applied to the philosophy of T. H. Green (Prolegomena to Ethics), who finds all reality to consist in 'intellectual relations.' (J.M.B.)

Intellectualism (aesthetic). Emphasis upon the intellectual content or ideal element in the aesthetic object, and the derivation of aesthetic value from this element. It is contrasted with SENSUALISM (q.v.) and FORMALISM (q.v.), and especially with emphasis upon the emotional aspects of aesthetic value. The theory of Hegel represents an intellectualistic tendency (see BEAUTY, IV). Cf. also RATIONALISM.

Literature: BERGMANN, Über das Schöne (1887). See also under the topics referred to above. (J.H.T.)

Intelligence: see INTELLECT.

Intelligible: see LATIN AND SCHOLASTIC TERMINOLOGY, Glossary, 'intelligibilis'; and mundus intelligibilis under MUNDUS; also cf. Eisler, Wörterb. d. philos. Begriffe, 'Intelligibel.' (J.M.B.)

Intemperance: see TEMPERANCE.

Intension (in logic): for foreign equivalents see COMPREHENSION (in logic), with which it is generally in modern logic taken as synonymous.

The name is derived from the scholastic use of the term intentio. On the history of the word see Baynes, New Analytic, ii. 92. (R.A.)

Intensity (measurement of mental): see WEBER'S LAW, and FECHNER'S LAW, and cf. the following topic.

Intensity (mental) and Intensive Magnitude [Lat. in + tendere, to stretch]: Ger. Intensität, Stärke (strength, applied rather to stimulus), intensive Grösse; Fr. intensité, grandeur intensive; Ital. intensità, quantità intensiva. Intensive magnitude is a kind of quantity, inasmuch as it admits of the distinction of more and less. Besides saying absolutely that what possesses intensive magnitude exists or does not exist, we can say that it exists in various degrees. On the other hand, it is held to be distinguished from extensive quantity or magnitude, because the difference between one intensity and another cannot be exhibited as a separate intensive magnitude; whereas the difference between one extensive magnitude and another is itself an extensive magnitude.

In the gradual transition from blue to green, through intervening blue-greens and green-blues, each colour in the series is bluer than that which follows it and greener than that which precedes it. Such differences of more and less are intensive. If a green-blue be regarded as a compound of green and blue, such intensive variations may be described as variations in the relative degrees of green and blue. If the sensation called a green-blue is regarded as simple, the intensive variation must be supposed to affect merely the relative degrees of resemblance of the green-blue to pure green on the one hand and pure blue on the other. On either hypothesis the term degree is preferable to intensity. Degree may be used to denote all kinds of intensive magnitudes. But it seems convenient to give the term intensity a more restricted application. It means more especially that intensive quantity of sensation which is a function of the quantity of physical energy expended in its production. Thus a sound, without varying in pitch, may vary in intensity (loudness) according to the amplitude of the vibrations which affect the organ of hearing. On the other hand, variation in pitch, with approximately unaltered loudness, is a variation in intensive magnitude or degree, but not in intensity.

It is a question how far, if at all, the intensity of sensation is revivable in the corresponding mental image. Most psychologists assume that the difference is only one of degree. Others, like Lotze, say that mental images do not possess intensity at all.

It has been maintained, by Münsterberg and others, that intensity does not belong intrinsically to the sensation which is said to be more or less intense, and that it is not really an intensive magnitude. On this view, what we take for an intensive quantity is in truth the extensive quantity of some concomitant experience (kinaesthetic according to Münsterberg).

Others regard intensive distinctions as really not quantitative mentally, but in all cases qualitative. See QUANTITY, QUALITY, and PSYCHOPHYSICS. (G.F.S., J.M.B.)

Literature: the textbooks of psychology and treatises on psychophysics; KANT, Krit. d. reinen Vernunft (Eng. trans., Müller), 136. (J.M.B.)

Intent (psychical): Ger. Meinen (nearest; cf. Eisler, sub verbo), Sagen-Wollen, im Sinne haben; Fr. intention; Ital. intento (cf. foreign equivalents given for CONTENT and INTENTION). What intelligent consciousness 'means or intends' (James).

The word is not in general use in this sense. But some term is needed, and 'intent' seems peculiarly appropriate. The intent of consciousness at any moment is virtually identical with the object of consciousness at that moment. But the word 'intent,' in the application we propose, marks a certain point of view from which the object may be regarded.

In any process having unity of interest there must also be corresponding unity of object. If our interest be merely in attaining more full, definite, or vivid knowledge, the object as it becomes more perfectly known must be identified as the same with the object as less perfectly known. Hence it can be regarded in two aspects. As the process advances, the object progressively receives or tends to receive further specification. Any any moment its detail is only partially presented. Yet these partial presentations come before consciousness as appearances of one and the same total object which it is endeavouring to know in its completeness. Now this total object, considered as the goal of conscious endeavour, may be called with great appropriateness the intent of consciousness. For it is what the mind consciously means or intends, but has not yet attained. The same remarks apply to the case in which the interest involved is practical -- in which there is an endeavour after the production of some result other than mere knowledge. The end pursued becomes progressively defined in the process of its achievement. So far as it is as yet indefinite, and therefore only partially developed in consciousness, it is an 'intent.'

The word CONTENT (q.v., 2) has sometimes been used in a sense more or less analogous to that which we propose for intent (i.e. by Bradley). But this usage is unfortunate. In the first place, the intent is precisely what consciousness does not contain. In the second place, the phrase 'content of consciousness' has a different application in current usage. It is applied to all special modifications of conscious experience, whatever may be their nature, and not merely to objects of consciousness. Indeed, it is sometimes questioned whether we ought to apply it to objects at all. In perceiving the distance of things in space, the experiences connected with movements of the eyes play an important part. These experiences are contents of consciousness; but they are not objects. We do not perceive them. What we do perceive is the external object and its spatial relation. Again, when we are pleased or displeased with anything, the pleasure or pain is a content of consciousness. But it is by no means always an object or an intent of consciousness. It only becomes so if, and so far as, we reflect on our subjective state. The same holds true of the self. There are always present in consciousness contents which belong to the self as distinguished from the not-self. But we are not always thinking of ourselves. Self-consciousness may be present in every moment of our waking lives. But the consciousness of self as a self is not invariably present. Finally, it would be correct to speak of the content of a 'merely feeling-consciousness' in the sense in which that phrase is used, among others, by T. H. Green. But it would not be correct to speak of such a consciousness as having an intent.

In relation to allied conceptions we may remark that the intent is the consciousness of the general nature of the END-STATE (q.v.) of an intellectual process before it is reached; and in mental progress toward an IDEAL (q.v.) we have successive stages of 'intent.' (G.F.S.- J.M.B.)

Intention [Lat. in + tendere, to stretch]: Ger. Absicht; Fr. dessein; Ital. intenzione. The purpose in view in any action, along with all the consequences of the action, so far as foreseen to be certain or probable.

The distinction in any act of intentio, actio, and finis is found in Gregory I (540-609 A.D.): cf. Ziegler, Gesch. d. christ. Eth., 247. The definition above given agrees with that of Sidgwick (Meth. of Eth.). The intention is thus the action from the internal or agent's point of view; and the internal character of morality is brought out by laying emphasis on the intention rather than on the external results or consequences. Intentions have been distinguished as immediate or remote, outer or inner, direct or indirect, conscious or unconscious, formal or material. See J. S. Mackenzie, Manual of Ethics (3rd ed.), 60, 61. (W.R.S.)

The best German usage of Absicht seems to be in agreement with this, the distinction between means and ends (Zwecke) being marked. Absicht is the end for which there may be alternative means (Meinong, Psych. - eth. Untersuch. zur Werttheorie, 94, 95; Höfler, Psychologie, 473, 518). Where, according to Meinong (loc. cit.), the end is directly pursued, without means, Absicht becomes Ziel -- a usage not general, however. Cf. DESIGN, and see TERMINOLOGY (German). Intention, in the broader ethical sense of entire moral INTENT (q.v.), a determination of disposition or character, is rendered by the German Gesinnung (Höfler, loc. cit.). (J.M.B.)

Intention (first and second, in philosophy) [Schol. Lat. intentio, prima et secunda]. Used in a series of scholastic distinctions (both intentio and intentionalis), for which see LATIN AND SCHOLASTIC TERMINOLOGY, 13, 14; revived in modern philosophy to indicate the distinction of knowledge as direct (first) and reflective (second) intention. See INTENTION (in logic), and cf. REFLECTION.

Literature: HODGSON, Philos. of Reflection, Index; citations in EISLER, Wörterb. d. philos. Begriffe, 'Intentio'; GOCLENIUS, Lex. Philos., 253. (J.M.B.)

Intention (in law). The purpose of an act; it is often imputed, without regard to its actual existence.

A man acts at his peril. If loss to another naturally ensues from his voluntary act, he is liable, although it is neither intended by him nor due to his negligence (Holmes, The Common Law, 82; Holland, Jurisprudence, chap. viii. 93; Pollock, Jurisprudence, chap. vi. 138). Crime rests on intention; but he who does a criminal act is held to have intended the actual and natural result, although in fact he may have intended only a much less grave offense. Contracts rest on agreement, presupposing an intent to assume an obligation, but the law often implies the intent. 'Such an intent may be implied, although it be certain that it never actually existed, but not unless the parties are in such relations that each ought to have had it' (Beers v. Boston and Albany Railroad Co., 67 Conn. Law Reports, 425). Cf. RESPONSIBILITY (legal).

Literature: authorities cited above; also BENTHAM, Mor. and Legisl. i. chaps. vii, xii. § 2. (S.E.B.)

Intention (in logic) [Lat. intentio, with the same meaning in Aquinas (Summa Theol., I. 9. 53, is the principal passage); in classical writers an act of attention (and so Aquinas, ibid., I. ii. 9. 38, art. 2, and elsewhere); from in + tendere, to stretch. Aquinas seems sometimes to use the term for a mode of being (ibid., I. ii. 9. 22) and sometimes for a relation (ibid., I. 9. 29 art. 1; 9. 76, art. 3, and esp art. 4)]. A concept, as the result of attention.

First intentions are those concepts which are derived by comparing percepts, such as ordinary concepts of classes, relations, &c. Second intentions are those which are formed by observing and comparing first intentions. Thus the concept 'class' is formed by observing and comparing class-concepts and other objects. The special class-concept, ens, or what is, in the sense of including figments as well as realities, can only have originated in that way. Of relative second intentions, four are prominent -- identity, otherness, co-existence, and imcompossibility. Aquinas defined logic as the science of second intentions applied to first. (C.S.P.)

Interaction [Lat. inter + actio, action]: Ger. Wechselwirkung; Fr. interaction; Ital. interazione. (1) The relation between two or more relatively independent things or systems of change which advance, hinder, limit, or otherwise affect one another.

(2) The relation of mere uniform occurrence of such systems together.

An important case of supposed interaction is that of MIND AND BODY (q.v.), in the discussions of which interaction is usually used in the first sense (under the phrase influxus physicus). The theory of PRE-ESTABLISHED HARMONY (q.v.), which holds that mind and body are absolutely independent -- their changes merely occurring together -- sometimes construes interaction in the second sense, while retaining the term (in English). The more general application is to the relation of objects which 'act and react' in the external world. Cf. MUTUALITY, and RECIPROCITY (for which interaction is sometimes used as translation of the term Wechselwirkung in Kant's table of categories).

Literature: books on metaphysics. The classical citation is LOTZE, Metaphysics, Bk. I. chaps. v, vi. A late discussion is in ORMOND, Foundations of Knowledge, Pt. II. chap. vii. (J.M.B.)

Intercession [Lat. intercessio, from intercedere, to pass between]: Ger. Fürbitte; Fr. intercession; Ital. intercessione. (1) the office undertaken by Christ on his ascension into heaven, of perpetual mediation before the Father in behalf of those whom he had redeemed by his death. (2) Prayer offered by saints in heaven to God or Christ in behalf of persons still on earth or in purgatory.

The intercession of Christ is a common doctrine of all Christians, while that of the saints is an accepted article in the creeds of the Roman and Greek Catholic churches only. Some traces of belief in the efficacy of the intercession of the saints may be found among Protestants, but with the rejection of prayer to the saints as idolatry, belief in their intercessory function largely disappeared. (A.T.O.)

Interdependence: see DEPENDENCE, and RECIPROCITY.

Interest [Lat. interest, it concerns]: Ger. Interesse; Fr. intérêt; Ital. interesse. (1) The consciousness which accompanies mental tendencies of any sort, so far as they terminate upon mental objects or stimulate to the construction of them.

Considered in abstraction from the content or object upon which the tendency or disposition goes out, interest is usually considered a phase of feeling, and classed with the 'intellectual feelings.' Interest is always manifested by voluntary attention, to which it may be considered a stimulus, or of which it may be considered a result. 'Exploring' interest, or 'interest of curiosity,' is often distinguished from interest of 'custom,' habit, or preference; the former seeming to be more of the nature of a stimulation to intellectual function, and the latter a result of frequent function. This latter aspect it is which underlies the popular use of the term in the plural, 'interests' meaning prevailing and more permanent dispositions. We suggest that the distinction be marked by the terms 'actual' and 'dispositional' interest.

(2) Loosely used for personal advantage or good; as in the phrase 'it is in his interest to do so.' This meaning is not sufficiently exact to be technically useful. For the pedagogical doctrine of interest see below.

Literature: the general works on psychology and pedagogy. Special discussions of the psychology of interest are in the larger psychologies of JAMES, SULLY, and BALDWIN. (J.M.B.- G.F.S.)

Interest (doctrine of, in education). The doctrine that the interest naturally attaching to the ends for which pupils study should be awakened in the means (i.e. the studies) used for reaching them; and, conversely, that permanent interest in the ends should be fostered through the means.

When interest attaches to the end, but not to the means for reaching it, we have drudgery, as in the case of a workman who thinks only of the dollar, taking no pride or interest in the labour that earns it; on the other hand, when there is interest in the means but none in the end, we have play, not work. Interest is then only amusement. When, however, there is interest in the end to be attained by activity, and also in the means for reaching the end, we have the type of work desirable in education. A direct interest, therefore, should be aroused in the studies as the means of reaching the ends of education; this interest when thoroughly aroused has a reflex influence in developing true ideals of life and conduct. The mental attitude of the sculptor is the ideal one for the pupil, since the interest he feels in the statue as an end attaches to every stage of its creation. When this direct interest is moral as well as intellectual and aesthetic, then instruction becomes truly educative. See EDUCATIVE INSTRUCTION, and DISPOSITION.

Literature: HERBART, Sci. of Educ. (trans. by Felkin), 122-99; ZILLER, Allg. Päd., 330-89; McMURRY, Gen. Meth., 49-68; DE GARMO, Herbart and the Herbartians, chap. v; DEWEY, Interest as related to Will (2nd suppl. of the First Year-book of the Herbart Society); HARRIS, Professor Dewey on Interest and the Will, Educ. Rev., May 1896; Herbart's Doctrine of Interest, Educ. Rev., x. 71; BARNES, A Study of Children's Interests, Stud. in Educ.; SHAW, A Comparative Study on Children's Interests, Child-Study Mo. (July-August No., 1896); LUCKEY, Children's Interests, North-Western Mo., vii. 67, 96, 133, 156, 221, 245, 306, 335; BALDWIN, Story of the Mind, chap. viii; ARDIGO, Sci. dell' Educ. (1897). (C.DE.G.)

Interest (in economics): Ger. Zins; Fr. intérêt; Ital. interesse. A payment for the use of capital; habitually expressed in terms per cent. per unit of time.

Payments in this form were regarded with grave disfavour by the canon law, and were veiled under the forms of compensation for loss suffered by the owner of the capital while it lay in others' hands; or also of a fictitious rent-charge (Ger. Zins, Census). But the historical starting-point of the modern interest system seems to be found in the contract of assurance whereby some of the partners in an enterprise would virtually insure the others against industrial risks (compare Ashley, Eng. Econ. Hist.).

The practical justification of interest is to be found in the large amount of capital which can be utilized by this motive, and the relatively small price which the community has to pay for the results achieved. The theoretical justification is more difficult. Some have sought to base it on the abstinence of the capitalist; others on the productivity of the capital. These productivity theories of interest were in past generations for the most part rather crude; under the influence of the Austrian theory of value they have been made extremely complex (compare Wieser, Natural Value). Still others (Jevons) have laid stress on the economic value of time as a basis of interest. Boehm-Bawerk's theory, which is perhaps the most influential one at the present day, is to be regarded as a development of the latter view.

It may be questioned whether the thing which these these authors explain has any very close connection with the commercial phenomenon of interest, which is really an average or commutation of profits rather than a marginal increment of productivity.

Literature: BOEHM-BAWERK, Kapital und Kapitalzins (trans. into Eng. by Smart), a work of monumental excellence. (A.T.H.)

Interference [Lat. inter + ferire, to strike]: Ger. Interferenz; Fr. interférence; Ital. interferenza. (1) If two sound-waves of the same length are travelling in the same direction, we have a strengthening of the sound when the phases are coincident, and a neutralization of sound when they differ by half a wave-length. These phenomena are termed phenomena of auditory interference (Helmholtz, Sensations of Tone, 160). See BEATS.

(2) Similar phenomena arise from the interference of light-waves (visual interference). Many natural colour effects, among them iridescence, are due to the interference of rays reflected from thin films (see Tyndall, Light, 1885, 61).

(3) The word interference is used analogically of the mutual inhibition or cancellation of physiological or mental processes, as judged by the results (see Bergström, Amer. J. of Psychol., v. 356, vi. 433). Similar conceptions are the Vorstellungsconcurrenz of the Herbartians, and the 'interference of imitation waves' discussed by Tarde, Les lois de l'imitation, 26 ff. See INHIBITION. (E.B.T.)

Intermediate State: Ger. Zwischenzustand; Fr. état intermédiaire; Ital. stato intermedio. The condition of souls during the interval between the death of the body and the final consummation or last judgment.

The belief in an intermediate state is a feature of Platonism, which connects it with the transmigration cycle. The Stoics also believed in state of soul-existence after the death of the body, which was to continue till the end of the cycle of cosmic existence to which it belonged when it ceased to exist. The consummation, then, was to be dissolution. There is, properly speaking, no intermediate condition in Hindu eschatology. The soul perishes at death, and only Karma survives to lead to a reincarnation. The soul does not properly exist in the interval. Of the Christian confessions, the Roman Church teaches distinctly the existence of an intermediate state of purification (purgatory) for those who die penitent. Reformed Christianity does not dogmatize on the subject, though the condition of the soul between death and the judgment is conceived to be different from its condition after that event. Cf. HADES, and PURGATORY. (A.T.O.)

Intermittence Tone [Lat. inter + mittere, to send]: Ger. Intermittenzton, Unterbrechungston; Fr. son (ton) d'intermittence; Ital. suono (or tono) d'intermittenza. If a tone is interrupted at short intervals (by passing a card, e.g., to and fro between a tuning-fork and the ear), we have artificial BEATS (q.v.); if, then, the intervals are made short enough, we have not beats, but a new tone, called the intermittence or interruption tone. The tone is theoretically important, as suggesting the origin of combination tones in rapid beats.

Literature: HELMHOLTZ, Sensations of Tone, 533; KÖNIG, Quelques Expériences d'acoustique, 139; MAYER, Amer. J. of Sci., 3 ser., viii. 241, and Philos. Mag., xlix. 352, 428; WUNDT, Physiol. Psychol. (4th ed.), i. 473, 476; EBBINGHAUS, Psychologie, i. 312. (E.B.T.)

Internal [Lat. internus]: Ger. inner; Fr. interne; Ital. interno. As applied to an individual experience the term has certain implications: (1) That conscious experience is in some way inside the body, and is so contrasted with things external to the body, and in more refined thought with the body itself (when the 'something inside the body' comes to be identified with the brain). (2) That individual experience, as such, is unshared by other individuals, and is so contrasted with external objects which can be present to different persons. (3) That the consciousness of experience is direct or immediate as opposed to the 'indirect' apprehension of external things through the medium of the sense. See discussion under EXPERIENCE; and cf. INTROJECTION, and KANT'S TERMINOLOGY (6, 7). (G.F.S.- J.M.B.)

Internal Speech (and Song): Ger. inneres Sprechen (und Singen); Fr. parole (et chant) intérieure; Ital. parola or linguaggio (e canto) interni, endofasia (Morselli). The content when speech is mentally revived with or without actual utterance. (J.M.B.- G.F.S.)

It indicates the class of mental states denoted popularly by the phrases having something to say 'in mind,' 'musing,' 'having tunes in one's head or ear' (internal song), together with the part played by such internal revivals in actual speech or song. Cf. KINAESTHETIC EQUIVALENTS. For the defects of speech which arise from the disturbance of this function see SPEECH (defects of), and AMNESIA. The adoption of Morselli's term Endophasia in English, French, and German (Endophasie) is recommended, and with it the term Endomusia is suggested for internal song (melody).

Literature: STRICKER, Ueber die Bewegungsvorstellungen; BALLET, La Parole intérieure; SÉGLAS, Les Troubles du Langage chez les Aliénés; JANET, Automatisme psychologique, and Rev. Philos., Nov., 1892; BASTIAN, Brain as Organ of Mind; STUMPF, Tonpsychology, i. Also (together with internal song): EGGER, La Parole intérieure; STRICKER, Langage et Musique; WALLASCHEK, Vtljsch. f. Musikwiss. (1891), Heft 1, and Zeitsch. f. Psychol., vi. Heft 1; LOTZE, Medicinische Psychol., 480; G. E. MÜLLER, Grundlegung d. Psychophysik, 288; BRAZIER, Rev. Philos., Oct., 1892; BALDWIN, Ment. Devel. in the Child and the Race, chap. xiv, and Philos. Rev., ii. (1893) 389 (in the last three many titles are given); MORSELLI, Semej. malat. ment. (1895). The literature of APHASIA may also be consulted. (J.M.B., G.F.S.)

International Law: Ger. Völkerrecht, Fr. droit international; Ital. diritto internazionale. The body of rules generally observed by civilized, sovereign states in their dealings with each other, and with one another's citizens or subjects. Less correctly termed the law of nations. D'Aguesseau was the first to remark that it was a law between nations, rather than a law of nations (Œuvres, ii. 337). Private international law: see CONFLICT OF LAWS.

The ius fetiale in ancient Rome was the law expounded by a priestly college, which determined the circumstances under which hostilities might be commenced against a foreign power, the forms of declaring war, &c. It was only a law for Rome. International law first grew into form under the hand of Grotius, mainly through his Mare Liberum (1608) and De Iure Belli et Pacis (1624), and received this name from Bentham (Morals and Legislation, chap. xvii. § 25).

Literature: VATTEL, Le Droit des Gens, &c.; WHEATON, Elements of Int. Law; PHILLIMORE, Int. Law; HAUTEFEUILLE, Des Droits des Nations neutres, &c.; FIELD, Draft Outlines of an Int. Code; BLUNTSCHLI, Das moderne Völkerrecht, &c.; CALVO, El Derecho Int.; WOOLSEY, Introd. to the Study of Int. Law. (S.E.B.)

Interpretation (in law) [Lat. interpretatio]: Ger. Interpretation, Erklärung; Fr. interprétation; Ital. interpretazione. The process of fixing the application of legal rules in particular cases (Pollock, Jurisprudence, 219, 224-5). It is legal or authoritative when it is the work of the proper representatives of the state; doctrinal when it is a mere matter of grammatical or logical construction proceeding from a private individual. In England and the United States the judicial interpretation of the law on any point, by the highest court, is itself law, but only as an official statement of what the law is and was before the decision upon that point (Markby's Elements of Law, § 72).

In Roman law interpretation was ordinarily sought in the first instance from jurisconsults holding no official station, and their opinions, certified for use in court, were received as authority. In the early empire a legal sanction was given to such opinions, when proceeding from certain persons who were invested with the ius respondendi, or found in certain treatises. In countries following the principles of the civil law, judicial precedents, in the line of interpretation, have little weight except that due to their intrinsic reasonableness.

Literature: PUFFENDORF, De Officio Hominis et Civis, i. chap. xvii, de Interpretatione; WOLFF, Inst. of the Law of Nature and of Nations, ii. chap. xix, de Interpretatione; LIEBER, Hermeneutics; DWARRIS, Statutes and Judicial Interpret.; BON, Instituzioni del Diritto pubblico internazionale. (S.E.B.)

Intersubjective [Lat. inter + subiectus, thrown under]; Ger. intersubjectiv; Fr. intersubjectif; Ital. intersuggettivo. (1) Applied to 'intercourse' between different consciousness at any stage of their development (Ward, Naturalism and Agnosticism).

(2) Applied to what is immediately present in each individual consciousness (was jeder in seinem Bewusstsein unmittelbar vordindet; Volkelt, Erfahrung und Denken, 42; quoted by Eisler, Wörterb. d. philos. Begriffe, sub verbo). (J.M.B.)

Interval [Lat. intervallum, a space between]: Ger. Zwischenzeit, Intervall; Fr. intervalle; Ital. intervallo. (1) The time between two concrete events abstracted from the intervening events: a duration concretely determined.

Psychologically, an interval is always determined as a relative function of the events from which it is abstracted; objectively, an interval is determined by a controlled series of events (chronometric devices). (J.M.B., G.F.S.)

(2) In experiments upon the temporal consciousness: the 'filled' or 'empty' duration lying between two limiting stimuli. See TIME SENSE.

Literature: (to 2): on the 'just noticeable interval' see MACH, Sitzber. d. Wien. Akad., 2, li. 142; EXNER, Pflüger's Arch., xi. 403; HAMLIN, Amer. J. of Psychol., vi. 564; WUNDT, Physiol. Psychol. (4th ed.), ii. 390 ff.; WEYER, Philos. Stud., xiv. 616, xv. 67. (E.B.T.)

Interval (in music). A musical term for difference of pitch between two tones. 'When two notes have different pitch numbers there is said to be an interval between them' (Helmholtz, Sensations of Tone, 13).

The intervals of the musical scale are sharply defined, and have, besides their distinctive names ('octave,' 'fifth,' &c.), various technical characterizations, as harmonic and melodic, simple and compound, augmented and diminished, consonant and dissonant, &c. Psychophysics has borrowed the word 'interval' from music, but employs it more freely, with sole reference to vibration ratios (Stumpf, Tonpsychologie, ii. 135). (E.B.T.)

Intoxication [Lat. intoxicatus, poisoned]: Ger. Berauschung; Fr. enivrement; Ital. intossicazione. (1) The effects of certain drugs or poisons.

(2) Frequently limited to alcoholic intoxication.

The state of intoxication usually makes itself felt soon after the absorption of the toxic substance. The mental symptoms which characterize it differ considerably according to the poison used; but a very typical characteristic is a state of excitement, release of inhibition, unrestrained conduct, inactivity, exaltation, incoherence. But these are only the characteristics outwardly most conspicuous; effects often differing from those just mentioned, and extending into less obvious alteration in mental processes, characterize the various forms of drug intoxication. These are described in general, and with regard to the more important intoxicants, under PSYCHIC EFFECT OF DRUGS. For the effects produced by alcohol, see ALCOHOLISM. For further details consult the works cited under those topics. (J.J.)

Intraselection [Lat. intra, within, + selectio]: Ger. Intraselection, Kampf der Teile (Roux); Fr. sélection interne; Ital. selezione interna. A process, held to be analogous to that of natural selection, by which the fittest cells, tissues, or parts within an organism prevail over others and ultimately supplant them.

Incidentally employed by Herbert Spencer in 1860 as an illustration in discussing social phenomena; the conception is generally attributed to Wilhelm Roux, 1881, and has been adopted by Weismann, to whom the term is due. Weismann thus summarizes: 'Just as there is a struggle for survival among the individuals of a species, and the fittest are victorious, so also do even the smallest living particles within the organism -- not only cells and tissues, but also the smallest living particles or "biophores" -- contend with one another, and those that succeed best in securing food and place grow and multiply rapidly, and so displace those that are less suitably equipped.' Weismann subsequently suggested the phrase 'histonal selection' for this process, and finally reached the hypothesis of struggle between the germinal elements. He speaks of the three principal stages of selection as (1) INDIVIDUAL (Ger. Personal-) SELECTION (Darwin and Wallace); (2) Histonal Selection (Roux); and (3) GERMINAL SELECTION (Weismann). See those topics; also SELECTION, and EXISTENCE (struggle for). The particular case of the selection of alternative functions, such as movements, has been called Functional Selection (see EXCESS).

Literature: HERBERT SPENCER, The Social Organism, Westminster Rev. (1860); W. ROUX, Der Kampf der Theile im Organismus (1881); A. WEISMANN, Effect of External Influences upon Development, Romanes Lecture (1894), and Germinal Selection, Monist (1895); DELAGE, La Structure du Protoplasma, &c.; BALDWIN, Ment. Devel. in the Child and the Race (2nd ed.), chap. vii. (C.LL.M.)

Intrinsic (1) and (2) Extrinsic [Lat. in- and extrinsecus]: Ger. innerlich (or wesentlich) and äusserlich; Fr. in- and extrinsèque; Ital. in- and estrinseco. (1) Necessarily, and (2) not necessarily, belonging to a thing or object of thought. (J.M.B.)

Intrinsic Value: Ger. innerer Werth; Fr. valeur intrinsèque; Ital. valore intrinseco. WORTH (q.v.) which belongs to an object or action in itself and is not due to its tendency to lead to some other object, or to promote a result. (W.R.S.)

Introjection [Lat. intro, within, + iacere, to throw]: Ger. Introjection; Fr. introjection; Ital. introjezione. The name given by Richard Avenarius to a certain theory, which he considers fallacious, of the relation between the cognitive consciousness of the individual and the external world cognized by it. This theory rests upon two assumptions: (1) that the individual consciousness is locally enclosed within the individual organism; (2) that its presentations of external things are merely internal images or copies of these things, taken to be so by reason of the process described below.

'Introjection' is closely akin to that 'ideal philosophy' which Reid ascribes to his predecessors, and in particular to Descartes, Locke, Berkeley, and Hume. There is no doubt that Reid was largely right in his account of the position of these philosophers. In the case of Descartes, we may refer to his theory of 'ideas' in the corporeal phantasy to which the mind directly applies itself, and which intervene between it and external things. Indeed, the whole of the Cartesian philosophy is dominated by the antithesis between 'ideas' as objects that lie exclusively within subjective consciousness, constituting its private property, and the world outside which these ideas are supposed to resemble or to which they correspond. Further, it is clear that Descartes is apt to confuse existence within the individual consciousness with existence within the individual organism. The soul is for him situated within the pineal gland, and it cannot directly cognize material objects unless they are in local proximity to it. As for Locke, we may refer to a passage quoted by Reid: 'Methinks the understanding is not much unlike a closet wholly shut from light, with only some little opening left to let in external visible resemblances or ideas of things without. Would the picture coming into such a dark room but stay there, and lie so orderly as to be found upon occasion, it would very much resemble the understanding of a man in reference to all objects of sight and the ideas of them.' The same kind of assumption is illustrated by Hamilton's theory that the primary qualities are perceived as 'in our organism,' and by his doctrine of sense-perception throughout (his ed. of Reid, ii. 881).

Avenarius describes and analyses this point of view with great precision, and he shows that it must emerge naturally and necessarily at a certain stage of mental growth. This feature of his theory has been considered especially original, and it is this to which many of the expositions of introjection as a process have been confined. He also shows the essential fallacy involved in it, and traces the disastrous consequences of this fallacy in philosophy and psychology. But Avenarius was anticipated, on the psychological side at least, by Herbart. Herbart, in his account of the growth of self-consciousness, traces the emergence of a point of view essentially the same as that which Avenarius calls introjection. 'The child at a certain stage comes to distinguish between those living things which contain within them representations of things external to them and those which do not.' This point of view is crude, but it constitutes an essential step in the development of the consciousness of self. The mode in which it originates will be most clearly exhibited by an example. 'A child sees a dog run away from a stick which is raised to strike it. He figures the stick as present to the dog, i.e. as in some sense inside the dog. Otherwise the dog would not run away (for in running away it is moved from within, not from without).' But it is obviously not the real stick which he thinks of in this way; for he sees the real stick outside of the dog. It is, therefore, an unreal stick, i.e. the representation or image or idea of the stick. For an image is that which is like a thing and is nevertheless not the thing itself. Thus the child regards the dog as having a representation in the way of an image or copy of what is without it. This point of view, acquired in the first instance by observation of other living things, he easily and inevitably transfers to his own case, inasmuch as he comports himself towards external things in an essentially similar way. He is now, therefore, able to regard the various objects of his consciousness as representative images of something other than themselves. These images he can carry about inside him, whether the reality they represent is present to his senses or not. He thus has an idea of what an idea or perception is. It is the counterpart inside him of a thing outside him. The conception is crude and inaccurate, and will not stand the test of reflective criticism. But it is none the less an indispensable step in the development of self-consciousness (Herbart, Psychol. als Wiss., § 133). Avenarius gives the name introjection to the view which results from the carrying over to or into one's own body of this dualism between images and things.

As Reid waged war on the 'ideal theory,' so Avenarius wages war on the philosophical and psychological developments of 'introjection' as a point of view. He opposed to it the doctrine of 'essential co-ordination.' The self and the environment of which it takes cognizance are in direct and essential relation. The one cannot exist apart from the other. When a man says that he sees a tree before him, he means the actual tree, not an image of it. He means that he sees something outside him, not inside him. He ought to interpret the same words as used by another man in strictly the same sense. He ought to infer from them that the other man sees a tree outside him, and not a picture of the tree inside him. To adopt the second alternative is the fallacy of introjection. It is a fallacy because the interpretation of another man's words depends on the analogy of our own experience. But in our own experience the object as part of our own external environment is the object seen; and if we suppose it absent, the seeing of it is logically abolished also. Hence, in the case of the other man, we must infer that what he sees is part of his external environment, not a complex of sensations inside him (e.g. somehow localized in his brain) and 'projected' outside him. The fallacy of introjection does not end here. Avenarius, like Herbart, lays stress on the fact that the point of view gained first by a crude inference from the actions of our fellow men or of animals is transferred by a back-stroke to ourselves. Hence the introjection theory may be expressed in the general formula, 'all perceived parts of our environment -- as perceived -- are nothing but presentations in us' (R. Avenarius, 'Bemerkungen zum Begriff des Gegenstandes der Psychologie,' in Vtljsch. f. wiss. Philos., xviii. 143 ff.).

Literature: AVENARIUS, as cited, also Menschlicher Weltbegriff, and Krit. d. reinen Erfahrung. For a brief statement in English see WARD, Naturalism and Agnosticism, ii. 172; also BALDWIN (for a development somewhat similar), Ment. Devel. in the Child and the Race, chap. xi. § 3. (G.F.S.)

The point of view of introjection is defended (as against Avenarius) by Jerusalem (Urtheilsfunction; see also in Vtljsch. f. wiss. Philos., xviii. 170), who calls his own theory of judgment 'Introjectionstheorie.' See also the notice, with citations, in Eisler, Wörterb. d. philos. Begriffe, sub verbo. (J.M.B.)

Introspection [Lat. intro, within, + spectus, seen]: Ger. innere Wahrnehmung, Selbsbeobachtung; Fr. introspection, observation interne; Ital. introspezione, coscienza riflessa in sè. Attention on the part of an individual to his own mental states and processes, as they occur, with a view of knowing more about them.

Locke uses the term reflection for 'the notice which the mind takes of its own operations' (Essay, ii. chap. i. § 4). Other writers speak of an 'inner sense' or 'inner perception.' The suggested analogy to 'outer sense' and 'outer perception' is misleading.

Literature: see INTROSPECTIVE METHOD. (G.F.S.- J.M.B.)

Introspective Method: Ger.Methode der inneren Wahrnehmung (or Selbstbeobachtung); Fr. méthode introspective; Ital. metodo introspettivo. The systematic use of introspection for scientific purposes.

The introspective method is essential to psychology, and it has been followed by psychological writers in all ages, from Plato and Aristotle downward. A main advantage of the method of experiment in psychology is that it gives opportunity for introspection under test conditions. Some psychologists may be called introspective in a special sense, because they make more exclusive use of the method than others. Among these are St. Augustine, Hobbes, Locke, Berkeley, Hume, and the earlier English psychologists in general. But no psychologist ever confined his procedure to mere introspection. It was always more or less supplemented by inference from resulting products to producing processes, and by observation of the manifestations of mental process in other minds. Cf. PSYCHOLOGY.

Literature: BENEKE, Die neue Psychol., Aufsätze 1 und 2; HERBART, Psychol. als Wiss., Zweiter Theil, Erster Abschnitt, chap. v; BRENTANO, Psychol., chap. ii; JAMES, Princ. of Psychol., i. 115 f.; LADD, Psychol., Descrip. and Explan., chap. ii; VIGNOLI, La legge fondamentale dell' intelligenza (1876); VILLA, Psicol. contemporanea; and textbooks of psychology in general. (G.F.S.)

Intuition [Lat. intueri, to look at]: Ger. Anschauung, Intuition (see TERMINOLOGY, German, sub verbo); Fr. intuition; Ital. intuito, intuizione. (1) Sense intuition: the final stage in the mental determination of an external object, consisting in a synthesis of elements in space and time.

This meaning is in so far common with the philosophical meaning of intuition that it leaves open to analysis the discovery of the sensational and other elements which go into the determination, and in default of such analysis makes the intuition of objects an act of direct apprehension. See INTUITION (in philosophy).

(2) Motor intuition: ready command of a complex action or series of actions independently of conscious preparation; and the act itself considered as a motor synthesis.

Applied to the act itself which is thus performed; a phrase which corresponds to percept, the object of sense-intuition. Some writers use synergy for the process of motor synthesis itself, and synerg might be employed for the resulting action, co-ordinate with percept. This would be convenient in various discussions, such as the loss of impairment of the 'synerg' in apraxia, the relation of motor and sensory elements -- that is, of percept and synerg -- in all concrete determinations of objects. The adjective form, 'synergic,' would also lend itself to use.

Literature: sense intuition: see the general works on psychology and the titles given under EXTERNAL WORLD, PERCEPTION, and EPISTEMOLOGY. Motor intuition: besides the foregoing, see the titles under HABIT, SYNERGY, and APRAXIA; also WARD, Mind, July, 1893, and Oct., 1894; MÜNSTERBERG, Die Willenshandlung; MOSCI, Le forme dell' intuizione (1881). (J.M.B., G.F.S.)

Intuition (in educational method). Primarily, the grasp of knowledge through the use of the senses; concrete ways of apprehending knowledge.

The middle ages had departed far from sense methods of teaching; they emphasized the word or the symbol above the thing symbolized. Comenius and Pestalozzi brought the word of words and that of things into intimate relation again, by laying much stress on sense-perception in education. Herbart made a further advance by urging the importance of apperception. The perception itself is important only when fully apprehended. Cf. METHOD.

Literature: COMENIUS, The Great Didactic; PESTALOZZI, How Gertrude teaches her Children; BOWEN, Froebel, 4, 156, 159; ROSENKRANZ, Philos. of Educ., 76-81. (C.DE.G.)

Intuition (moral): Ger. sittliche Intuition; Fr. intuition morale; Ital. intuizione morale. The immediate apprehension, apart from experience, or moral principles or of the moral quality of action.

Whether there are any moral intuitions, in the strict sense of the term, is a question of controversy between intuitive and empirical writers; whether, if there are such intuitions, they are perceptions of the moral quality of particular actions, or of general principles of morality, is a question which divides the intuitionist writers themselves. See INTUITIONAL ETHICS. (W.R.S.)

Intuition (in philosophy): Ger. Intuition, Anschauung (see TERMINOLOGY, German); Fr. intuition; Ital. intuizione, intuito. Immediate or direct apprehension, perception, judgment, cognition, and the results of such processes.

The root-idea of this term is that of directness or IMMEDIACY (q.v., different forms) in contrast to abstractive or representative knowledge, or, more frequently, to forms of knowledge which are mediated by a discursive process. This fundamental idea appears in all, or nearly all, of the various senses in which the term is used.

(1) Of sense-perception: to denote its presumed immediacy; to denote perception proper as objective in contrast to sensation as subjective; to denote the perception of present objects in contrast to reproductive and productive imagination; to denote the perception of individual objects in contrast to conception and thought. Sensuous cognition in general is sometimes termed sense-intuition or intuitive knowledge. See INTUITION (second topic above). (2) Of self-consciousness as the perception of inner states (internal sense). Also, by many writers, of self-consciousness as the perception of the ego: see below, (5). (3) In aesthetics: to designate the act of aesthetic appreciation or contemplation, or the insight of the artist into aesthetic values. (4) Of cognition or knowledge: to denote sense-perception or self-consciousness, see above, (1) and (2); to distinguish intuitive knowledge, in which all the component elements can be directly presented, from symbolic knowledge (Leibnitz, Meditationes de Cognitione, Veritate et Ideis, 1684); to denote the immediate perception of the connection between subject and predicate, this connection being conceived as the essence of knowledge (Locke, Essay concerning Human Understanding, IV. ii. 1); to denote the knowledge of first truths, see below, (5). (5) To denote original, self-evident, and necessary first principles, both theoretical and practical, and the (primary) consciousness of them (Sir William Hamilton, Reid'sWorks, note A, v. 3; see also INTUITIONALISM). (6) By Kant, who distinguished between empirical intuitions of objects through sensation (empirische Anschauungen, intuitions a posteriori) and pure intuition (intuition a priori: space and time as the form of sensibility; Krit. d. reinen Vernunft, Werke, Hartenstein, 2nd ed., iii. 55-6, 60, 65). It is to be noted, however, that high authorities have of late questioned the equivalence of intuition and the Kantian Anschauung (E. Caird, The Crit. Philos. of Kant, 1889, i. p. xi; see also KANT'S TERMINOLOGY). (7) In the phrase intellectual intuition: to denote an immediate function of thought or understanding akin to the direct perception of sense. Such would be required, according to Kant, to secure a positive knowledge of things-in-themselves, while the absence of it is the condition which necessitates for human understanding the distinction between mechanism and teleology as well as between possibility and actuality, necessity and contingency (Werke, Hartenstein, 2nd ed., iii. 216-24, v. 408-23). Fichte ascribes to intellectual intuition the self-knowledge of the ego; Schelling makes it the medium of man's knowledge of the absolute (Philos. Briefe ü. Dogmatismus u. Kriticismus, viii). See also below, (8). (8) To denote the spiritual illumination of the mystics and the supernal vision of God. Intellectual intuition is used in this sense among the German mystics. The term without the adjective is employed also, by many writers who are not to be classed as mystics, to describe the moral and the religious consciousness considered as immediate organs of spiritual truth.

Literature: general works on philosophy and psychology; references under INTUITIONISM, and the other topics INTUITION; EISLER, Wörterb. d. philos. Begriffe, 'Anschauung.' (A.C.A.Jr.)

Intuitional Ethics: Ger. Intuitions-Ethik; Fr. morale (or éthique) intuitive (or intuitionniste); Ital. etica intuitiva. Any theory which recognizes moral intuitions. See ETHICAL THEORIES.

Intuitional ethics depends upon the assumption that man has a special faculty or capacity for recognizing moral distinctions. According to the different views held as to the nature and objects of this faculty, three main forms of intuitional ethics have been distinguished: (1) aesthetic or perceptional intuitionism, according to which the moral value of particular actions and affections is apprehended intuitively either singly (as held by Shaftesbury and Hutcheson) or relatively to one another (as in the view of Martineau, Types of Ethical Theory, 1885, that motives or stimuli to action form a sort of moral hierarchy, in which the preference of a lower to a higher is always condemned, and the preference of a higher to a lower always approved by conscience); (2) dogmatic intuitionism (the common scholastic theory, and the view of Butler in his Dissertation on Virtue, of Richard Price and Thomas Reid, and more recently of McCosh and Calderwood), according to which the rightness or wrongness of classes or kinds of actions -- or, as some writers hold, of classes or kinds of motives -- is intuitively known; (3) philosophical intuitionism, in which a complete synthesis of practical rules is sought, and the practical reason or conscience is held to lay down one universal rule capable of distinguishing good from evil (e.g. the categorical imperative of Kant). Cf. Sidgwick, Meth. of Eth., I. vi, viii; III. (W.R.S.)

Intuitionism or Intuitionalism: Ger. Intuitionismus; Fr. intuitionnisme; Ital. intuizionismo. (1) These terms are sometimes employed to describe that form of ethical and religious philosophy which looks on the moral and the religious nature as immediate organs of spiritual truth. See INTUITION (in philosophy), 8.

(2) They are also used in designation of systems of philosophy which are based upon an (assumed) intellectual intuition of absolute reality. See INTUITION (7).

(3) They are employed most specifically, and most frequently in the history of later modern thought, to denote the philosophy which makes knowledge and life dependent on a body of immediately given self-evident and necessary first truths. See INTUITION (5).

These last constitute the fundamental principles alike of theory and of practice. They are held to be independent of experience, in that they are not derived from it nor established by it, but supply it with a basis and with norms, and so make it possible. Associationism, on the contrary, looks on these principles and their apparent evidence as products of experience; while evolution, enlarging the doctrine of associationism by the addition of heredity, views them as native to the individual but developed in the race (Spencer, Princ. of Psychol., § 208; Princ. of Eth., §§ 40-7). The intuitive first truths are variously enumerated by different writers. All intuitionalists may be said to include under the first principles of knowledge the formal (concepts and) judgments which make up the organic framework of thought, although the list is variously drawn (the causal principle is, perhaps, the one which is postulated with the nearest approach to universality after the first principles of logic and mathematics). Others, and especially the members of the Scottish school, add to these principles judgments (or perceptions) of content, maintaining, for example, that there is an immediate, self-evident, and necessary knowledge of external reality, or, at least, that sense-perception includes such a factor among others, that self-consciousness supplies a direct and indubitable cognition of the ego, &c. The existence of intuitive first principles of religion is also asserted, but less frequently: the majority of intuitionalistic thinkers, for instance, now recognize that there is no immediate intuition of God.

Cf. INTUITIONAL ETHICS, A PRIORI, ASSOCIATIONISM, COMMON SENSE, INNATE IDEAS, INTUITION, REALISM, SCOTTISH PHILOSOPHY, and TESTS OF TRUTH.

Literature: TH. REID, Intellectual and Active Powers; Sir WM. HAMILTON, Reid's Works, note A; J. S. MILL, Exam. of Hamilton's Philos.; J. McCOSH, The Scottish Philos., The Intuitions of the Mind, and Realistic Philos.; H. CALDERWOOD, Handb. of Mor. Philos.; H. SIDGWICK, Meth. of Eth. iii; J. MARTINEAU, Types of Ethical Theory ii; R. FLINT, Theism, 79-86, and Appendix X. (A.C.A.Jr.)

Besides the Scottish philosophers proper -- and their successors -- by whom the intuitional philosophy has been developed under that name, a point of view essentially intuitional has been held by certain French realistic thinkers (Laromiguière, Maine de Biran, Cousin, Janet) who were influenced directly by Reid. A similar influence has coloured philosophy in America (McCosh, Porter, Hopkins). Intuition has further lent itself in turn to the uses of theological philosophy, both Catholic and Protestant, most conspicuously again in Scotland and the United States, in both of which countries, however, the intuitionalistic and realistic point of view is rapidly yielding to certain forms of idealistic thought. (J.M.B.)

Intuitive Morality: see INTUITION (moral).

Invagination [Lat. in + vagina, a sheath]: Ger. Einstülpung; Fr. invagination; Ital. invaginazione. The inpushing or folding process whereby a simple cell-layer may more or less completely enclose a cavity.

In development many organs arise by invagination, and the hollow vesicle or BLASTOSPHERE (q.v.) is thus generally converted into a two-layered cup or GASTRULA (q.v.).

The generalization that the formation of a two-layered BLASTODERM (q.v.) is typically produced by the invagination of a hollow spherical one-layered vesicle is due to Haeckel. See GASTRAEA THEORY.

Literature: HAECKEL, Generelle Morphol. (1866); F. M. BALFOUR, Compar. Embryol. (1880); and the citations given under EMBRYO. (C.LL.M.- E.S.G.)

Invariability: see VARIABLE, and UNIFORMITY.

Invention [Lat. in + venire, to find]: Ger. (1), (3) Erfindung (Erdichtung), (2) Erneuerung (Barth); Fr. invention; Ital. invenzione. (1) In psychology: a relatively new determination in the sphere of imagination and thought, judged by the thinker to be true or valuable.

Inventions are, in a general way, distinguished from mere fancies, on the one hand, by their acceptance as true or valuable; and they are more than the reinstatement of old thoughts, being 'relatively new.' Narrower restriction of the term would bring it within the range of controversy. Some of the questions which arise about invention are: the distinction of inventions from other sorts of mental constructions within the so-called imaginative function; the process of selection of inventions as true or valuable; the mechanism in general whereby relative novelty is reached; the plane of attainment from which the particular invention is projected; the relative independence of the individual thinker in appraising his inventions, as over against the influence of social suggestion. The terms SELECTION (mental), SELECTIVE THINKING, DETERMINATION (mental), RELATIVE SUGGESTION, &c. (see those terms), are used for the progressive advance of the inventive process through successive stages. The process of reaching inventions is also called invention.

Considerable literature has been devoted to the development of the child with more particular reference to his active life. The principles of his activity had heretofore seemed to fall under one or other of the two principles of invention and imitation; and in so far as they were considered separate and independent types of action, the child's conduct was interpreted in one category or the other. There was no common meeting-place for these two types. This is the older view; a view set in the usages of language itself, which contrasts strongly the imitative, copying, uninventive action (and child) with the inventive, self-active, spontaneous action (and child). This contrast as usually made is, however, too sharp. The recent psychological analyses of the child's activities show that imitativeness and inventiveness are really two phases of all action; that the terms are expressions of emphasis rather than of real and vital difference.

The first consideration which tends to diminish the degree of separation between an imitative and an inventive action concerns the definition of IMITATION (q.v.) itself. A more adequate analysis of imitation has shown that we cannot limit that term to the intentional conscious procedure of the child by which he closely observes some other person and then himself carries out the action which that person performs before him. In the first place, many imitations are performed without the child's consciously observing the model or knowing that he is acting with reference to a particular deed of another. Again, it is not necessary that the child should imitate another person, or another thing, than his own self. When he looks at his own hands accidentally placed in this position or that, or at any attitude of his into which the circumstances of the time may have forced him, these he may imitate, aiming to do intentionally or spontaneously what was done before by his members accidentally or by external constraint. So also he may imitate his own mind as well as his own body. When he has before him something to imitate -- that is, before his mind -- it does not matter whether there be or be not outside of him another person actually doing the thing he is imitating. It may be that the model he aims to reproduce is the result of his own thought, imagination, fancy. Suppose a child opening his mind in the early morning, as he lies in bed in the dark, and thinking over the doings of the preceding day. Something of a striking character comes into his mind from the preceding day's sport, and he proceeds to jump from his bed and perform the act again and again. In this case he is imitating his own action of the preceding day, or -- if we interpret his present state -- he is imitating the image or memory which has arisen in his mind spontaneously. All this is so plainly the same sort of action as that in which the model is set up by some one else, that it is now called 'self-imitation.' Whenever the child thinks of anything he can do, and then proceeds to do it in a way which reproduces a result like that of which he thinks, then he is imitating, and his act is self-imitation.

When we come to inquire into invention, we get a result which at once brings that form of action into connection with self-imitation. The old idea that the mind can create things, ideas, plans, &c., 'out of whole cloth,' so to speak, has been given up. We now know that the mind, even that of the great genius, is held down to the actual store of materials which he has acquired in his lifetime. He must call up from the stores of his memory images, earlier thoughts, reminiscences of action, &c., which are 'fit' to go into the scheme of his invention. 'Imagination never creates' has now become a proverb, and recent advances have tended in the direction of making it more than ever true.

So what the inventor does is really to meditate on what he already knows, to consider the possibilities of new combinations of the data with which he is already so familiar. That is the reason we never hear of a farmer inventing an electric light, nor of a statesman getting rich by taking out patents for new machines. Each invents only in the field in which he has worked so thoroughly and so long that his mind is stored with knowledge, both of facts and of principles. This means that the inventor must, as a preliminary, fall into the state described above as one of self-imitation. He must bring up before his mind materials already familiar, to be used as a more or less adequate copy for the new construction which he is to make. He must cause to pass before him this and that possible combination, this and the other possible situation, in order that his sense of fitness may go forth critically for the selection of the more available.

Putting together the two points now made, we see that the relation of invention to imitation is very close indeed. The child, or the man, must be a facile imitator before he can be an inventor. He must become an adept in the methods of using his materials of memory and imagination. He must by constant self-imitation practise the combinations he already knows, and by so doing come to see the possible forms of novelty into which the materials may be cast.

Furthermore, the study of children has shown that the connection between these functions is even closer than this. We find that the child goes on to invent largely in proportion as he actually carries his imitations out into action. He sets out to reproduce something which another person or his own fancy suggests, and just by carrying out this purely imitative purpose he falls into new ways of action or thought which seem to him more valuable. This is especially true when the function in question allows of large variations; when the hand is used or the tongue -- members which, by their great flexibility, give various possibilities of modified result. The child soon learns these possibilities, being to use his imitative functions with view to securing variations on the models, and loves to produce relatively new and inventive results. So, too, as he becomes strenuous, using his members vigorously and with less exact control, the performance flows over the limits of the model, so to speak, and gives to the result new and possibly valuable phases.

The general conclusion, therefore, is that the child is not 'either an imitator or an inventor'; on the contrary, he is always in some degree both at once. Teachers tend sometimes to disparage the imitative scholar in contrast with the more inventive one. But this is generally a mistaken attitude. Imitation is the natural schoolmaster to invention. Imitation may, of course, be made parrot-like, a matter of mere repetition, especially when the teacher approaches it with such a disparaging attitude. But the average scholar is dependent upon imitation for the normal growth of his faculties -- more, much more, upon than upon any other one factor -- and the recognition of the essential union of imitation and invention which psychology now teaches is, in the teacher's hand, the best means of furthering this progress.

(2) In sociology: any relatively new idea which gains currency in society. For the part assigned to invention by current sociological theories see SOCIAL ORGANIZATION (also for literary references).

(3) A mechanical device for utilizing power, doing work, &c. The popular distinction between invention and discovery -- the former giving something not found in nature, and the latter something realized in nature -- is only partially justified from a psychological point of view.

The German term Erdichtung is applied to the more poetic and fanciful, and so to the less strictly true, and even to the false, productions of the imagination. It is more nearly equivalent to the English fancy or imagination in the phrases 'drawing on the imagination,' 'fanciful fabrication,' &c., a meaning expressed in the terms 'practising,' 'romancing,' &c., which do not imply intentional deception. The German Erneuerung is suggested by Barth (Philos. d. Gesch. als Sociol., i. 212) to include both invention (3) (Erfindung) and discovery (Entdeckung).

Literature: (psychological): PAULHAN, Rev. Philos.; ROYCE, Studies in Good and Evil, chap. ix, and Psychol. Rev., v. (1898) 113; JAMES, The Will to Believe, 216 f., 255 f.; STOUT, Analytic Psychol., Bk. II. chap. vi; SIMMEL, Arch. f. syst. Philos., i. 34 ff.; BALDWIN, Soc. and Eth. Interpret., Pt. II, and Psychol. Rev., January, 1898. (J.M.B., G.F.S.)

Invention (in anthropology): see INVENTION (in psychology), particularly meaning (3), as depending upon or arising from meaning (1). (J.M.B.)

The anthropologist's interest in invention lies in its relation to mental evolution, as indicated by an increased utilization of natural resources for comfort and material prosperity, for the arts and sciences, for the pleasures and civilization of life. In the early history of human invention is thus contained the beginning of that struggle for human supremacy which constitutes the true culture history of mankind. The directions which such studies of the evolution of invention have taken are various: on the material and industrial side may be mentioned the arts and implements concerned with the cultivation of the earth, with the elaboration of fibrous textures for clothing, with war and the chase, with the preparation of food; the habitations of man in cave and shelter, in tent and hut and house; the transportation of man and goods by land and sea. On the mental side may be mentioned the development of the social life through the invention of money and a system of barter; the development of writing and drawing; the inventions of art and decoration, of music and the dance, the composition of poetry, myth, and tradition; the discoveries of nature's laws; the means of counting and weighing and measuring, and other rudiments of scientific lore.

The history of invention likewise suggests the problem of individual variation. The capacity for independence and originality is always opposed by the conservative tendencies in society and the power of the status quo. The psychology of invention considers the determining factors in such original variations, and the processes which constitute or promote it.

Literature: general treatises on ANTHROPOLOGY (q.v.) and the history of CULTURE (q.v.). Also especially O. T. MASON, The Origin of Invention (1895); discussion in Psychol. Rev., v. 1, 113, 307; GROOS, The Play of Man (Eng. trans.), on play-experimentation as a factor in invention (orig. p. 55); SOURIAU, Théorie de l'Invention; RIBOT, L'Imagination créatrice (1901); PAULHAN, Psychol. de l'Invention (1901). (J.J.)

Inversion (sexual): see PERVERSION (sexual).

Invertebrate [Lat. invertebratus, without vertebrae]: Ger. wirbellos; Fr. invertébré; Ital. invertebrato. Applied to any animal not belonging to the sub-kingdom of vertebrates.

Originally it was supposed that the presence or absence of a vertebral column was a sufficient diagnostik mark. It is known now that the lowest undoubted members of the true vertebrata have no vertebrae, the vertebral axis being replaced by the notochord and its fibrous sheaths (marsipobranchs, i.e. lampreys, &c.); but their entire structure proves that these animals are closely related to the vertebrates only, and not to any invertebrate, hence the term invertebrate is still used with the original limitations, although in the strict etymological sense it is not correctly applied. (C.S.M.)

Investment [Lat. investire, to invest]: Ger. Kapitalanlage; Fr. placement; Ital. investimento. The use of capital with a view to profit; also, the form which the capital takes when thus used.

Looking at the transaction from the private standpoint, a property owner transfers a certain amount of money either to labourers or to other property owners, in the hope of receiving a larger amount of money in the future by the sale of products acquired or made. Looking at it from the public standpoint, the property owners as a class put the labourers in a position to consume the wealth over which the property rights have extended, in the expectation that the products of the labour to which they thereby acquire rights will more than replace the wealth thus consumed. In practice, the term investment is chiefly applied to permanent investments like real estate or securities. (A.T.H.)

Invisible World: see WORLD.

Involuntary (Action, &c.): Ger. (1) widerstrebend; Fr. (1) contre-volontaire (suggested); Ital. (1) controvolontario (or antagonistico), (2), (3) involontario. (1) Action contrary to an actual volition, or to a volition which would have existed had there been time and opportunity to form it: contra-conative action. (2) NON-VOLUNTARY (q.v.) or aconative action. (3) NON-VOLITIONAL (q.v.) action, i.e. action which is not due to an express 'fiat' of the will.

Meaning (1) is recommended in accordance with the scheme given under ACTION. (G.F.S.- J.M.B.)

Involuntary Action (pathological): Ger. unwillkürliche Thätigkeit; Fr. action involontaire; Ital. azione involontaria. In a pathological sense an involuntary action is one which takes place in spite of the effort of the will to prevent it, thus implying some defective state of control or inhibition. Such states are considered under WILL (defects of). (J.J.)

Involution [Lat. in + volvere, to roll]: Ger. Involution; Fr. involution; Ital. involuzione. A term of SYMBOLIC LOGIC (q.v. borrowed from algebra, where it means the raising of a base to a power. In logic it has two different senses. (1) Relative involution: let lwm denote any lover of a well-wisher of a man. That is, any individual A is denoted by lwm, provided there are in existence individuals B and C (who may be identical with each other or with A), such that A loves B, while B wishes well to C, and C is a man. Further, let l^wm denote any individual A, if, and only if, there is in existence an individual C, who is a man, and who is such that taking any individual B whatever, if B is a well-wisher of C, then A is a lover B. The operation of combining l and w in this statement is termed 'progressive involution.' Again, let l^wm denote any individual A, if, and only if, there is in existence an individual B, who is loved by A, and who is such that taking any individual C whatever, if C is wished well by B, then C is a man. The operation of combining w and m in this statement is termed 'regressive involution.' These designations were adopted because of the analogy of the general formulae to those of involution in the algebra of quantity.

These kinds of involution are not, at present, in use in symbolical logic; but they are, nevertheless, useful, especially in developing the conception of continuity. These two kinds of involution together constitute relative involution.

(2) Non-relative involution: consisting in the repeated introduction of the same premise into a reasoning; as, for example, the half-dozen simple premises upon which the Theory of Numbers is based are introduced over and over again in the reasoning by which its myriad theorems are deduced. In exact logic the regular process of deduction begins by non-relatively multiplying together all the premises to make one conjunctive premise, from which whatever can be deduced by using those premises as often as they are introduced as factors, can be deduced by processes of 'immediate inference' from that single conjunctive premise. But the general character of the conclusion is found to depend greatly upon the number of times the same factor is multiplied in. From this circumstance the importance and the name of non-relative involution arise. (C.S.P.)

Ionics: see PRE-SOCRATIC PHILOSOPHY (Ionics).

Ire: see WRATH.

Irenaeus. Born probably in the first quarter of the 2nd century A.D. One of the most important of the early church fathers. Educated under Polycarp among others, he became a presbyter at Lyons. In 177, upon the martyrdom of Photinus, he became bishop of Lyons. He championed orthodoxy against Gnosticism. The place and manner of his death are uncertain; possibly he suffered martyrdom in 202 or 203 A.D.

Iron Age: see SOCIALIZATION.

Irony [Gr. eirwn, a dissembler]: Ger. Ironie; Fr. ironie; Ital. ironia. Assumed ignorance with an implied conscious superiority. (1) Socratic irony: see SOCRATIC METHOD.

(2) Romantic irony: used by a set of writers (Schlegel, Tieck, Solger) to characterize an aesthetic standpoint which emphasizes the artist's or critic's self-consciousness as the only reality and standard, and from this position of superiority regards the world of so-called reality, with its laws, morality, &c., as futile, unreal, and illusory. This conception grew out of Fichte's emphasis upon the ego as the central principle of philosophy. The 'genius' as critic showed this irony by his exposition of the futility of the works criticized; as artist he should set forth characters or situations which bring out the futility of life and its supposed principles.

Literature: LOTZE, Gesch. d. Aesthetik in Deutschland (1868), 370 ff.; SCHASLER, Gesch. d. Aesthetik (1872), 779 ff.; HEGEL, Philos. of Fine Art (trans. by Bosanquet), 121 ff.; J. H. SCHLEGEL, Die neuere Romantik (1863). (J.H.T.)

Irradiation [Lat. irradiare, to radiate]: Ger. Irradiation, Ausstrahlung, Fr. irradiation; Ital. irradiazione. The lateral diffusion of nervous stimuli out of the path of normal discharge, as a result of which the excitation of one peripheral end-organ may excite other central organs than those directly correlated with it or anatomically related to it by direct nervous connection.

Where it takes place is not certainly known. Dogiel shows that in skin areas subject to great irradiation (genital organs) the end-organs of one order are connected by communicating rami, suggesting peripheral irradiation. There are also indications of irradiation of excessive stimuli in the spinal cord. The stimulus may not be excessive, but in that case the entire part of the system implicated is in a state of expectant innervation. It has been suggested that irradiation (or an analogous process) is at the foundation of all or most-pleasurable sensations (Herrick).

Literature: A. S. DOGIEL, Die Nervenendigungen in der Schleimhaut der äusseren Genitalorgane des Menschen, Arch. f. mikr. Anat., xli (1893); C. L. HERRICK, Modern Algedonic Ideas, J. of Compar. Neurol., v (March, 1895); also Wood's Ref. Handb. Med. Sci., ix (1893). (H.H.)

Irrational: see RATIONAL.

Irrational Action: Ger. unvernünftige Handlung (i.e. Handlung wider besseres Wissen); Fr. action irrationnelle; Ital. azione irrazionale. The choice of an action which (1) is opposed to what is objectively right or reasonable in the circumstances, or (2) is opposed to what the agent sees to be right or reasonable in the circumstances.

In both senses the phenomenon of irrational choice, or unreasonable action, has given rise to difficulties. The former difficulty, which is discussed by Aristotle (Eth. Nic., III iv) under the question whether it is the true or the apparent good that is the object of a man's wish, is not so much a difficulty concerning choice or activity, as the difficulty of understanding unreason at all -- how things can 'appear' other than they are, how error or false opinion is possible. The difficulty commonly referred to is the second, namely, to understand how knowledge and choice can be at variance in the same mind at any given time. The Socratic paradox that vice is ignorance is a denial of the existence of the phenomenon called incontinence or akrasia. This is analysed in detail by Aristotle, Eth. Nic., VII.

Literature: SIDGWICK, Pract. Eth., ix; BALDWIN, Social and Eth. Interpret., chaps. ix, x. (W.R.S.)

The confusion of the meanings (1) and (2) is very common (e.g. Kidd, Social Evolution); that which is irrational from the observer's or philosopher's point of view being treated as irrational also from the actor's point of view, when it may be simply non-rational, or even rational. See further discussion under RATIONAL, and SANCTION. (J.M.B.)

Irrelevant [Lat. in + relevare]: Ger. unanwendbar; Fr. sans rapport à, inapplicable; Ital. irrilevante. Not pertinent to the question. Irrelevant may be applied either (1) to the conclusion of an argument, which is erroneously taken to be decisive of the question, or (2) to any premise suggested which is declared to have no logical connection with the conclusion to which it leads. The former is identical with the ignoratio elenchi of the Aristotelian logic; the latter, a special form of confusion, includes the fallacy called by Aristotle non causa pro causa. See FALLACY. (R.A.)

Irreligion [Lat. in + religio, religion]: Ger. Religionsverachtung, Unglaube, Fr. irréligion; Ital. irreligione. A state of indifference or opposition to the theoretical or practical claims of religion.

It is to be observed of the term irreligion that it applies to an attitude rather than to any specific content, and is, therefore, more subjective than the term religion. It is privative rather than negative, and, like many privatives, has a positive force in English implying not merely the absence of the religious attitude from a being who normally possesses it, but also the presence of a different attitude, one of indifference or opposition. Irreligion is to be distinguished from unbelief or impiety, with which it may be associated, but which it does not necessarily include. Cf. Guyau, L'Irreligion de l'avenir (Eng. trans.), for a sociological defence of irreligion. (A.T.O.)

Irritability [Lat. irritabilis, irritable]: Ger. Reizbarkeit; Fr. irritabilité; Ital. irritabilità. Power of an active tissue, nerve, muscle, gland, to respond to appropriate stimulation. See EXCITABILITY, NERVE STIMULATION AND CONDUCTION, and LIVING MATTER. (C.F.H.)

Irritant [Lat. irritare, to excite]: Ger. (1) Reizmittel, (2) Reiz; Fr. (1) irritant, (2) stimulant; Ital. (1) irritante, (2) stimolo. (1) In physiology: an agent, chemical, mechanical, or acting through the nervous system, which causes inflammation. See STIMULANT. (C.F.H.)

(2) In neurology: that which excites irritability; a STIMULUS (q.v.). (J.M.B.)

Isidorus Hispalensis. (560-636 A.D.) A prominent and learned ecclesiastic of the Western Church. A Spaniard, he succeeded his brother as bishop of Seville. He was ranked as the fifth Doctor Ecclesiae for his great learning. In his Sententiarum libri tres he gathers together a large number of propositions by himself and others, depicting the entire doctrine of salvation -- a compendium of ecclesiastical doctrine of the time.

Islam: see MOHAMMEDANISM.

Isolation [Ital. isolare, from Med. Lat. insulare, to separate]: Ger. Isolirung; Fr. ségrégation; Ital. segregazione, isolamento. The separation of a group of organisms into two permanent groups by any means which prevents interbreeding. The term segregation is also much used.

Moritz Wagner, in 1868, drew attention to the importance of geographical isolation. Gulick and Romanes developed and extended the conception. Romanes divides the effects of isolation into two classes, APOGAMY (q.v.) and HOMOGAMY (q.v.). His theory of PHYSIOLOGICAL SELECTION (q.v.) involves isolation by the barrier of sterility. By regarding the survivors who mate together, and the organisms eliminated before they produce offspring, as two isolated groups, he brings natural selection itself under the category of isolation, a view not generally adopted. Gulick and Romanes contend that in the absence of isolation (other than natural selection) evolution is monotypic (without divergent lines from common ancestors), and that all polytypic (or divergent) evolution involves isolation.

The distinction between (1) discriminate and (2) indiscriminate isolation (homogamy and apogamy) is that between the dividing off of a group (1) having some common mark or character already which differentiates them from others, or (2) not having such a differentiating character. Gulick and Romanes hold to so-called accumulative segregation, leading to polytypic evolution, even in the second case, on the group that in the group separated off the average or mean of the characters would not be exactly that of the larger group from which they were divided off, and this difference would be cumulative under the operation of natural selection. This sort of isolation Weismann calls AMIXIA (q.v.). (C.LL.M.- J.M.B.)

One of the most important applications of isolation in the form called by Romanes Physiological Selection is that which finds in it the origin of the STERILITY (q.v.) of species inter se. (J.M.B.)

Literature: MORITZ WAGNER, Die Darwinsche Theorie u. das Migrationsgesetz (1868); Ueber d. Einfluss d. geographischen Isolirung (1870); J. J. GULICK, Divergent Evolution through Accumulative Segregation, Linn. Soc. J. Zool., xx (1887); G. J. ROMANES, Darwin and after Darwin, Pt. III (1897), criticized by BALDWIN, Psychol. Rev., v. (1898) 215 f. Expositions may be found in CONN, The Method of Evolution (1900), and HEADLEY, The Problems of Evolution (1901). (C.LL.M.- J.M.B.)

Issue [Lat. exire, to go forth, through Fr.]: Ger. Streitpunkt; Fr. issue; Ital. questione. A topic of discussion or controversy.

Recently given a quasi-technical meaning by James (The Will to Believe), who distinguishes issues of various sorts with reference to belief and conduct. (J.M.B.)

Itch (or Itching) Sensation: Ger. Kitzelempfindung; Fr. sensation de gale; Ital. sensazionedella rogna. See TOUCH SENSATION, and ORGANIC SENSATION.