Classics in the History of Psychology

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Definitions Da - Deq

Posted June 2000

Dabitis: see MOOD (in logic).

d'Ailly, Pierre: see D'AILLY under A.

d'Alembert, Jean Baptiste le Rond: see D'ALEMBERT under A.

Daltonism: Ger. Daltonismus; Fr. daltonisme; Ital. daltonismo. Partial colour-blindness; so called from John Dalton (1766-1844), the founder of atomic chemistry, who published an account of the phenomenon in 1794. See COLOUR-BLINDNESS, and VISION.

Literature: HELMHOLTZ, Physiol. Optik (2nd ed.), 359; DALTON, Mem. of Lit. and Philos. Soc. of Manchester, v. I (Oct. 31, 1794). The literature of colour-blindness begins with Tuberville, 1684. (E.B.T.)

Damiron, Jean Philibert. (1794-1862.) Born at Belleville on the Rhone, and studied under Victor Cousin in Paris. Befriended by Jouffroy, he taught various subjects in Paris, finally philosophy at the Sorbonne. He became an Academician before his death.

Damnation (eternal): see JUDGMENT.

Damnum absque Iniuria [Lat.]: Damage not due to wrong. One who suffers such damage has no cause of action. A man is not liable for any unintended, consequential injury, resulting from a lawful act, where he is chargeable neither with negligence nor folly (Morris v. Platt, 32 Connecticut Law Reports, 84). Nor is he liable for any loss which he may cause to another, by force of an inevitable accident: as in case he were blown through a shop window by a sudden gust of wind.

The Roman law gave an action for damnum iniuria datum, and iniuria included both willfulness and negligence as a cause of damage. (Dig., ix. 2, Ad Legem Aquiliam, 5, § 1; 30, § 3). Iniuria in its most general sense embraced 'omne quod non iure fit.' It included, as grounds of action, contumelia, culpa, iniquitas, iniustitia, and, of course, dolus (Just., Instit., iv. 4, De Iniuriis).

Literature: SOHM, Instit. of Roman Law, § 72; PHILLIMORE, Princ. and Maxims of Jurisprudence (1856), xii, xlii. (S.E.B.)

Dancing Mania: Ger. Tanzwuth; Fr. chorée saltatoire; Ital. mania saltatoria, coreomania. An abnormal and excessive tendency to rhytymic movements, especially to dancing, manifested under special circumstances as the result of nervous contagion.

While some affected may be predisposed by temperament to such affections, the extension of the mania at certain periods has been so vast that it must have included normal individuals as well. Two marked epidemics, characterized by the dancing mania, occurred in the 14th and 15th centuries in Germany. See CONTAGION (mental). The manifestations are of a choreic nature, and are sometimes spoken of as choremania (also choreo or choromania). In extreme cases the dancing, which is often of a violent spasmodic nature, continues until the subjects sink from exhaustion; their senses seem dazed, they become victims of hallucinations and seem driven by an uncontrollable impulse to continue the contortions and saltations. Cf. Hecker, Dancing Mania (trans. 1885). Similar observations have been made by Lasnet among the Sakalanes in Madagascar. See CHOREA. (J.J.)

Dante (or Durante), Allighieri (or Alighieri). (1265-1321.) Born at Florence, and died in Ravenna. The greatest of Italian, and one of the greatest of all poets. He received a liberal education under the tutelage of Brunetto Latini, becoming skilful in music and painting, as well as verse-making. An early love game him the poetic impulse, and the death of the object of his affection became a deep and abiding sorrow in life. He devoted himself to philosophy, studying in Paris, Padua, and Bologna. The Thomist, Siger, attracted him most. In 1302 he was exiled, for political reasons, from his native city. He became the guest of Can (Grande) della Scala, and later of Guido of Ravenna. His philosophy follows Albert (in physics) and Thomas (in politics and theology) very closely.

Darapti: see MOOD (in logic).

Darii: see MOOD (in logic).

Darwin, Charles Robert. (1809-82.) An eminent English naturalist. Born at Shrewsbury, England, he was educated in the grammar school at that place, at the University of Edinburgh, and at Christ's College, Cambridge. In 1831 he received the Bachelor's degree, and sailed with Captain Fitzroy in H.M.S. Beagle, to survey the coast of South America. He himself went as a volunteer naturalist. The voyage extended round the world, 1831-6. In 1842 he took up his residence in the village of Down, Kent, where he prosecuted his studies and researches. His work On the Origin of Species by Means of Natural Selection is most famous: it expounds the principle of NATURAL SELECTION (q.v.) -- discovered also by Wallace -- which has revolutionized the biological sciences. See also DARWINISM, NEO-DARWINISM, and EVOLUTION.

Darwinism [from Charles Darwin]: Ger. Darwinismus; Fr. Darwinisme; Ital. Darwinismo. The distinctive features of the theory of organic evolution proposed by Charles Darwin.

In popular speech the word Darwinism is used as equivalent to organic evolution in general, and the 'descent of man' in particular. In the works of evolutionists it is applied either (1) to the views set forth in Darwin's works, which lay the main stress on natural selection, but allow of the inheritance of acquired characters as subsidiary thereto; or (2) to the view which was distinctive of Charles Darwin: the theory of Natural Selection. The latter usage is preferable. See NEO-DARWINISM, NATURAL SELECTION, EVOLUTION, and EXISTENCE (struggle for).

Literature: CH. DARWIN, Origin of Species; A. R. WALLACE, Darwinism; ROMANES, Darwin and after Darwin; POULTON, Charles Darwin and the Theory of Natural Selection; F. DARWIN, Life and Letters of Charles Darwin. See also under EVOLUTION. (C.LL.M.)

Datisi: see MOOD (in logic).

Datum: see GIVEN (in logic).

Daub, Carl. (1765-1836.) A German theologian, the friend and follower of Hegel, with whom he stood in close agreement. He is 'the founder of Protestant speculative theology.'

David of Dinant. A Christian Aristotelian of the latter part of the 12th and early part of the 13th centuries. His doctrines were condemned in 1209, and again in 1215, by the Church. He probably received his philosophic impulse from Moorish commentators on Aristotle's works. His followers are called Davidists.

Davidson, Thomas. (1840-1900.) Born at Deer, Aberdeenshire, Scotland; educated at Aberdeen University; taught in schools in Great Britain, Canada, and St. Louis, Missouri. In 1875 he settled in Cambridge, Mass. He founded the Glenmore School for philosophical study at Keene, New Hampshire.

Day-blindness: Ger. Tagblindheit; Fr. nyctalopie; Ital. cecità diurna, emeralopia. A symptom rather than a distinct disorder, characterized by an inability to see clearly in strong light. Nyctalopia is also used.

It may be due to hyperaesthesia of the retina, and result in a clearer vision by dim light or at night, than in full daylight. In suddenly passing from darkness to bright light a transient form of normal day-blindness may be said to exist. The opposite condition is Night-blindness. See Fuchs, Textbook of Ophthalmia (trans. 1899), 496. (J.J.)

Day-dreaming: see REVERY.

Daymare [AS. day + Ger. Mahr, a spectre]: Ger. Oppressionsanfall; Fr. dépression (neurasthénique, &c.); Ital. incubo della veglia. A feeling of temporary distress or terror, similar to nightmare, but occurring in a period of wakefulness. It is difficult to assign a cause for the feeling, but it may be connected with a disorder of the cerebral circulation. See NIGHTMARE. (J.J.)

De Facto: see DE IURE.

De Iure [Latin]. Of right; authorized by law. The term is correlative to de facto, which is used to describe what exists in fact, but not of right. See CORPORATION. (S.E.B.)

The antithesis currently implies the ground or justification upon which a consideration rests. De facto indicates 'a condition, not a theory'; a situation which has the sanction of actual existence as opposed to that which has the sanction of law, morality, or theory, though not realized in fact. (J.M.B.)

Deaf-mutism [AS. deaf + ME. mewet, akin to Gr. mn, uttered with closed lips]: Ger. Taubstummheit; Fr. surdi-mutité; Ital. sordomutismo. Deaf-mutism, while signifying the combined presence of a defect in hearing and an inability to speak, more precisely refers to the condition in which defective hearing, congenital or acquired in early childhood, hinders or retards the development of speech.

The deaf-mute in typical cases is of normal intelligence, and has no abnormality of the vocal organs. It should be noted, however, that nervous and other defects are more than normally frequent in cases of deaf-mutism, owing to the fact that the condition which induced the deafness is apt to induce other defects. Cf. DEAFNESS AND THE DEAF.

The special relation that obtains between deafness and mutism is in accordance with the general principle that motor or expressive functions are developed under the guidance of sensory or receptive functions. The motor tendency comes from within, but the result of the co-ordinated activity is guided by some one of the sensory processes; we hear when we speak or sing, we see when we write or draw. See CONTROL SERIES. The natural stimulus which keeps active the vocal instincts of the child is the hearing of its own voice and the voices of others. The deprivation of this normal sensory guide brings with it, by mere inertia, a failure of development of the impulses to articulate. But we both feel and hear what we speak, just as we both feel and see what we write. We can write, though imperfectly, with the eyes closed, or learn to write in the absence of sight, and we can learn to speak in the absence of hearing. The mutism is therefore not absolute, but capable of moderate cultivation. See DEAFNESS AND THE DEAF. In the determination of mutism, the most important factor is the age at which deafness occurs. Mutism always ensues (unless corrected by training as just indicated) in cases in which the deafness is congenital or occurs in early infancy. The precise age has not been determined -- although a specially directed statistical investigation is capable of determining it -- at which the occurrence of deafness will entail mutism; but it is likely that if deafness occurs not earlier than the fifth to seventh year, speech will continue without special efforts; while if special efforts are made to encourage the speech faculties which are developed at a still earlier age (say from the second year onward), there is reason to believe that mutism could be avoided. However, in persons who have been long deaf, but who speak fluently, there is frequently an imperfection of articulation, and especially of modulation, which indicates the absence of the corrective tendencies of the ear. The degree of the deafness is likewise a most important factor in the determination of mutism. Even those with partial hearing may become mute, but on the other hand even a slight amount of hearing is an advantage in the acquisition of speech. Before modern methods of education were established almost all the deaf were mute, but the possibility of replacing the ear by the muscle-sense has been satisfactorily established, and thus has modified the relation between deafness and mutism. Many writers speak of the semi-mute in reference to those who have acquired a partial control of speech in the absence of hearing.

Literature: see under DEAFNESS AND THE DEAF. (J.J.)

Deafness and the Deaf [AS. deaf]: Ger. Taubheit (ein Tauber); Fr. surdité (un sourd); Ital. sordità (un sordo). Any impairment in the perception of auditory stimuli, sufficient to deprive the individual of the benefits of ordinary conversation and the sounds of daily life, is termed deafness. See HEARING (defects of).

It varies from a slight difficulty in hearing the ordinary tone of voice, to absolute insensibility to sounds. Those whose defect requires special modes of education are commonly spoken of as the deaf. The most important fact in regard to deafness is its association with dumbness or mutism, persons thus affected being termed the deaf-and-dumb, or deaf-mutes. The special nature of this connection is considered under DEAF-MUTISM (q.v.); but its existence must be constantly borne in mind in considering the status of the deaf, as must also the great tendency of deafness to be congenital (about sixty per cent.), with its further considerable tendency, when acquired, to occur in early childhood.

As in the case of the blind the two dominant interests in the study of the deaf are the educational and the psychological. The former (which is largely represented in the literature) is concerned mainly with the accounts of provisions maintained in various countries for the education of the deaf, the methods of instruction employed, and the status of the deaf as a class. The psychological interest is centred in the determination of the effects upon the other senses, the intelligence, and the general mental and emotional development which is brought about by the deprivation of this sense.

Inasmuch as an overwhelming portion of significant sounds are those of language, the modes of communication adopted by the deaf are at once an important psychological and educational factor. The realm of sound covered by music is lost to the deaf as colour is to the blind. These forms of communication are: (1) gesture language, (2) manual sign (and alphabetic) language, and (3) oral speech. The gesture language as used by deaf-mutes is an elaboration of the primitive and natural sign language, in which things and ideas are referred to by pantomime, imitation or suggestion of their distinctive characteristics, supplemented by a considerable number of conventional signs. While such language is in part individual, it is remarkable how well deaf-mutes and primitive people using sign-language can understand one another (Tylor), and how extensively and rapidly it can be employed by those skilled in the art. The finger-alphabet consists of an artificial series of positions of either one or two hands (the former far more usual and preferable), each position answering to a letter. These letters are rapidly formed, and with equal rapidity interpreted by the eye of the one addressed. In case of blind deaf-mutes, such letters can be formed in the palm of the hand and thus interpreted, but of course much more slowly. This language is thus a manual equivalent or articulate words in terms of movements instead of sounds. The oral method attempts to induce on the part of the deaf-mute the movements of the lips and voice by imitation of these movements as seen in speaking, and to cultivate the practice of reading the movements of the lips in others -- lip-reading. The capacity for training in this direction varies in different deaf-mutes, but the success of the method, especially when applied to young children, is unquestionable. When employed along with the manual alphabet it is called the combined method. Of the two parts of the process concerned, lip-reading is simply an interpretation of the visual accompaniments of articulation, of which many persons of defective hearing but normal articulation avail themselves in following a conversation. The speaking is guided by the muscle sensations induced by the position of the vocal organs, but this guidance is far inferior to that of the ear; hence the articulation of the deaf-mute, even in the best cases, is only approximately correct, while the defective intonation and modulation produces a harsh and somewhat unpleasant effect. In the case of Helen Keller, who is completely blind and deaf, it has even been possible to educate the articulation without the aid of the sight of the lips, by means of the muscle sensations conveyed to her hands, which are placed upon the throat and lips of the speaker. See BRIDGMAN, LAURA, AND KELLER, HELEN.

In all respects, both psychological and educational, the age at which deafness occurs is highly important. The earlier the age the more serious the defect; while of course those who lose their hearing in late childhood or later retain their articulation. The degree of deafness is also important; the retention of even slight hearing constituting a considerable advantage.

As regards intellectual and emotional effects of deafness, it is often maintained, although without adequate investigation, that while in respect to ordinary occupations the deaf person is almost normal (more so than the blind), his lack of a ready communication with his fellow men is apt to induce a relative isolation, and a tendency to a morose, unsocial disposition. (J.J.)

Literature: MYGIND, Deaf-mutism (trans., 1881); T. ARNOLD, Education of Deaf-mutes (1888); A. G. BELL, Facts and Opinions relating to the Deaf (1888); J. HEIDSICK, Der Taubstumme und seine Sprache (1889); J. KITTO, The Lost Senses (1860); BELL, Methods of Instructing the Deaf (1898); E. A. FAY, Marriages of the Deaf in America (1898, with bibliography); H. H. HUBBARD, Deaf-mutism (1894); GELLI, Audition (1898); URBANTSCHITSCH, Ueber Hörübungen bei Taubstummheit und bei Ertaubung im späteren Lebensalter (1895); J. K. LOVE and H. ADDISON, Deaf-mutism (1896); E. WALTHER, Handb. d. Taubstummbildung (1895). (J.J. - L.M.)

Deafness (mental or psychic): Ger. psychische Taubheit; Fr. surdité mentale (or psychique); Ital. sordità mentale (or psichica). A condition analogous to MENTAL BLINDNESS (q.v.), affecting the understanding and interpretation of sounds.

It is distinguished from ordinary deafness by the retention of the power to hear sounds; what is lost is the power to appreciate the significance of the sounds. Inasmuch as by far the largest part of auditory interpretation lies in the realm of words and music, mental deafness (also known as mind-deafness) assumes the forms of word-deafness and musical deafness, or TONE-DEAFNESS (q.v., also AMUSIA). These defects often involve defects of MEMORY (q.v.). Cf. SPEECH AND ITS DEFECTS. (J.J.)

Deanthropomorphism [Lat. de, and Gr. anqrwpoV, man, + morfh, shape]: Ger. Deanthropomorphismus; Fr. and Ital. not in use. 'A progressive purification of theism' (Romanes) by an elimination from the idea of God of human attributes: the opposite of ANTHROPOMORPHISM (q.v.). The term is used by Fiske, Cosmic Philosophy, and Romanes, Contemp. Rev., July, 1886. (J.M.B.)

Death (physiological) [OE.]: Ger. Tod; Fr. mort; Ital. morte. Final cessation of the vital functions. Death of the body (somatic death) occurs when one or more functions (respiration, circulation, excretion, nervous co-ordination) become disturbed to such an extent as to render the harmonious working of the various organs impossible.

A tissue is said to die when it loses permanently its power of responding to its appropriate stimuli. The brain and nervous system die, in man and warm-blooded animals, at the moment of somatic death; gland tissue dies very soon after. Smooth muscle retains its irritability 45 minutes, skeletal muscle some hours, after death. (C.F.H.)

If by 'natural' death is meant the cessation of the existence of an individual organism as such, then death occurs universally among organized beings, since sooner or later they all cease to live as individuals, either themselves undergoing dissolution, or giving rise by some method of reproduction to other individuals. But by death is more generally meant the cessation of the processes of life, transforming a living being into a corpse. The question then arises, whether such death is an inherent property of living substance, or has been gradually evolved in the course of evolution. Weismann urges that, since in the lower unicellular plants and animals reproduction takes place by simple fission, generations following each other without the formation of any corpse, death does not here occur, and these organisms are, in a limited sense of the word, immortal. In the higher forms, where differentiation takes place between reproductive and somatic or body cells, the former only are perpetuated, and the latter sooner or later after reproduction cease to live, and so give rise to a corpse. Weismann holds that death has been developed by natural selection, because long-continued life of the individual subject to injuries from its environment, would no longer be of use to a species capable of sexual reproduction. Other observers, like Minot in the case of the higher organisms, and Maupas in the case of the unicellular infusoria, argue that senile decay or atrophy occurs in the life of all individuals or asexually reproduced generations, and would always ultimately lead to death, were it not for the rejuvenating influence of amphimixis. That this is the case with the majority of multicellular organisms can hardly be doubted. Whether this view is true of all unicellular organisms is still uncertain. It must be remembered that the potato has been reproduced by cuttings since its first discovery, and that sexual reproduction is unknown among many fungi and the bacteria. See AMPHIMIXIS, AGAMOGENESIS, SEX, and GERM-CELLS.

Literature: A. WEISMANN, Essays upon Heredity, &c. (trans. 1892), ii; M. VERWORN, Gen. Physiol. (trans. 1899); Y. DELAGE, Structure du Protoplasma, &c. (1895); E. MAUPAS, Recherches expérimentales sur la Multiplication des Infusoires ciliés, Arch. Zool. expér. et gén., vi (1888). (E.S.G.)

Death (spiritual): Ger. geistiger Tod; Fr. mort spirituelle; Ital. morte spirituale. (1) A condition of alienation from God, such as is noticed in several passages of the New Testament.

(2) Often taken to imply annihilation, when considered from a theological point of view, but spiritual death means more correctly the second, or "intensified," death, which is the ultimate doom of the deliberately godless, or grace-rejecting. As such, it includes the conceptions of eternal perdition, without hope of resurrection, and of eternal loss of happiness, with all the horror consequent thereupon. See ESCHATOLOGY.

On the whole the probability is that the conception is originally Jewish.

Literature: WEBER and SCHNEDERMANN, Jüdische Theol.; GEBHARDT, Doctrine of the Apocalypse, 291 (Eng. trans.); ALGER, Doctrine of a Future Life; SALMOND, Christian Doctrine of Immortality. (R.M.W.)

Decadence (social): Ger. Verfall; Fr. décadence; Ital. decadenza. See SOCIAL RETROGRESSION. (F.H.G.)

Decalogue [Gr. deka, ten, + logoV, word, reason]: Ger. Dekalog; Fr. décalogue; Ital. Decalogo. The law of the Ten Words, otherwise called the Testimony (Exod. xxv. 21), the Covenant (Deut. ix. 9), and the Ten Commandments. It is given in two versions (Exod. xx. 2-17; Deut. v. 6-21).

The miraculous details connected with the accounts of its promulgation, and the extremely composite nature of the texts containing them, have given rise to numerous critical problems, which cannot yet be regarded as solved by any means. It may be said, however, that, of the two versions, the former is esteemed the older and more authoritative, although Wellhausen dissents, and much weight is given to his view by Meisner. Some critics hold that the Decalogue could not have been formulated prior to the conception of religion developed by the prophets, and that, therefore, it is not earlier than the 8th century (Vatke, Wellhausen, Nöldeke, Smend, &c.); others that it has a Mosaic substratum, to which additions were afterwards made (Kuenen, Montefiore, Kittel, &c.); others that it is substantially Mosaic, but that interpolations, in the way of amplifications, have been made (Ewald, &c.).

The Decalogue is of the highest importance for the history of ethics and religion. It brings prominently forward, almost for the first time, the characteristically social nature of both. The community (Allgemeinheit), which plays so prominent a part in modern discussions of these subjects, is here emphasized. Its limitation lies, of course, in its predominatingly negative character, which is probably traceable to the fact that it was intended, in the first instance, as a condemnation of practices rife among the Semitic tribes at the time of its promulgation.

Literature: articles in the Encyc. Brit., and in Herzog's Real-Encyc.; EWALD, Hist. of Israel (Eng. trans.), ii. 18 f., 158 f.; KUENEN, Rel. of Israel (Eng. trans.), i. 285 f.; WELLHAUSEN, Comp. d. Hex., 331 f.; SMEND, Lehrb. d. alttest. Religionsgesch., 139 f.; BAENTSCH, Das Bundesbuch, 92 f.; MEISNER, Der Dekalog; DRIVER, Literature of the O. T., and Deuteronomy; SCHULTZ, O. T. Theol. (Eng. trans.); KITTEL, Hist. of the Hebrews (Eng. trans.); GEFFKEN, Ueber d. verschiedenen Eintheilungen d. Decalogus u. d. Einfluss derselben auf d. Cultus; B. BAUER, in Zeitsch. f. specul. Theol. (1838); LEMME, Die religionsgeschichtliche Bedeutung d. Decalogs. (R.M.W.)

Decay (in biology): see DEGENERATION (in biology), and DEVELOPMENT.

Deceit: see LIE, and EQUIVOCATION.

Deceptive Reasoning: see REASONING.

Decision [Lat. de + caedere, to cut]: Ger. Entschliessung. Entschluss; Fr. décision; Ital. decisione. The selective DETERMINATION (q.v.) of an end for action by choice between alternatives. Cf. Höfler, Psychologie, 518.

Wundt distinguishes between Decision, as a function of selective choice (Wahlhandlung), and RESOLUTION (q.v.) made for future voluntary action (Willkürhandlung). Judd (trans. of Wundt's Elements of Psychol.) uses decision as equivalent to Entschliessung. (J.M.B.)

Declarative: see PREDICATION, and PROPOSITION.

Declension [Lat. declinatio, a bending aside]: Ger. Declination, Wortbeugung; Fr. déclinaison; Ital. declinazione. Modification of form in nouns, adjectives, and pronouns by which they are enabled to express the relations of case. In the so-called inflectional languages the noun-forms serve not only to name the objects of thought, but also, chiefly through their endings, to denote the relations they bear in the sentence to the nucleus of the thought or statement, i.e. the verb.

The term had its origin in the grammatical system of the Greeks; klisiV, from klinein, to lean, was translated into Latin as declinatio. The various inflections were regarded as deflections from the upright as represented in the leading form. Thus the nominative was called the 'upright' case (enqeia, casus rectus), the others 'oblique' (plagioi). The cases are so many 'fallings' (ptwseiV, casus, from cadere, to fall). The Indo-European mother-speech was provided with seven different groups of noun-forms for the conventional expression of the most important relations within the sentence. Thus the nominative indicated the substantive idea, in connection with which the action of the sentence as expressed in the verb was concretely set forth, and received its psychological shape. The accusative served as the complement of the verb by giving its action direction and a point of application. The genitive indicated a whole, of which a part was affected by or involved in the governing word. It was the case of the genus or greater whole, and was hence named by the Greeks h genikh ptwsiV. The ablative indicated the source of the action of the verb. The dative indicated that which the action concerned. The locative indicated the place or the sphere within which the action took place. The instrumental expressed accompaniment, and hence means. In the separate languages the number of cases was generally reduced, a single case-form often assuming the functions of two or more. Such syncretisms are generally due to confusion of the case-functions in use, rather than to a blending of form.

Literature: B. DELBRÜCK, Vergleichende Syntax, i. 181 ff. (B.I.W.)

Decorative Art [Lat. decoratus, from decus, ornament]: Ger. decorative Kunst, Zierkunst; Fr. art décoratif; Ital. arte decorativa. (1) Art which aims rather to heighten the aesthetic value of some aspect of a larger whole than to embody aesthetic value in an independent construction. It includes personal adornment (cosmetic) and ornamentation, especially that of architecture and utensils, by drawing, painting, or carving. Its canons are 'adaptation, significance, and abstraction or conventionalization' (Collingwood). (2) Used by Véron as equivalent to formally beautiful art, as opposed to expressive art. This is not to be recommended, as the other usage has been constant.

Literature: COLLINGWOOD, The Philos. of Ornament (1883); MORRIS, The Lesser Arts of Life (1882); GROSSE, The Beginnings of Art (1897); VÉRON, Aesthetics, vii; BALDWIN, Social and Eth. Interpret., § 100; HADDON, The Evolution of Art (1895); SEMPER, Der Stil in den technischen und tektonischen Künsten (1878-9). See also CLASSIFICATION (of the fine arts). (J.H.T.)

Decrees (divine): see FOREORDINATION.

Decretum salutis. One of the 'Divine Decrees' according to the system of Calvin. It is closely connected with the dogma of election, and with the decretum reprobationis; all are intimately bound up with the dogma of original sin, the consequent 'plan of salvation,' and they played a leading part in the controversy on SUPRALAPSARIANISM (q.v.).

Literature: CALVIN, Institutes, iii. chaps. xxi f. See CALVINISM. (R.M.W.)

Decurtate Syllogism: see SYLLOGISM.

Decussation [Lat. decussatio]: Ger. Faserkreuzung; Fr. décussation; Ital. incrociamento. The crossing of fibre-tracts of the central nervous system at the median plane in such a way that the terminations of a given tract are in centres of different orders, while the crossing tracts are bilaterally symmetrical (see COMMISSURE). A decussation differs from a commissure, in that commissural fibres are supposed to connect homologous centres; but strictly, all commisural fibres appear to decussate, for, if the fibres are neurites, one end originates in a cell and the other terminates in a free arborization about a cell of a different layer.

In practice a decussating fibre is one which obviously connects centres of different orders on opposite sides. See BRAIN, and SPINAL CORD. (H.H.)

Deductio: see DEDUCTION, and METHOD (logical).

Deduction [Lat. de + ducere, to lead]: Ger. Deduction; Fr. déduction; Ital. deduzione. The type of mediate inference in which a conclusion is put forward as being implied in the propositions which are taken as data.

The essential mark is the necessity wherewith the conclusion is taken to follow from the understanding of the data and the combination of their contents. The name is applied either to the process of developing in thought and combining data, or to the represented relation between data and conclusion, or to the conclusion itself. The kind of relation involved leads naturally to the common definitions of deduction as reasoning from the general to the particular, or from the containing while to the contained parts, neither of which is sufficiently accurate. For Deductive Method, see METHOD.

It is only in modern times, mainly among English logicians, that the term has been employed to name one distinctive form of reasoning, contrasted from the outset with induction. Deductio, in its first technical use, was a translation of Aristotle's term apagwgh, and somewhat in this sense it still keeps a place in modern logical terminology in the phrase Reductio per deductionem ad impossibile. The ancient, mediaevel, and most commonly used terms to indicate what is now called deduction were syllogism and demonstration. (R.A.)

Deduction (in education). In instruction, deduction is a less rigorous process than in science, being used chiefly to form anticipations of further experience; or, as with Herbartian writers, who use the term loosely, to imply a wide application of derived generalizations to appropriate new particulars. See METHOD (in education).

Literature: HARRIS, Psychologic Foundations of Education, 62-89; DE GARMO, Essentials of Method, chap. v; JEVONS, Princ. of Sci. (C.DE.G.)

Defect (ethical): see FAULT, and VICE.

Defect and Defective (mental) [Lat. defectivus, imperfect]: Ger. Defekt (psychischer); Fr. défectuosité (mentale); Ital. deficienza (mentale). The term defective refers to classes of persons who lack some of the sensory or mental or moral capabilities which are characteristic of normal individuals. Such a lack is a defect.

The class would thus include (a) those with marked sensory defects, sufficient to characterize the individual as abnormal, i.e. mainly the blind and the deaf; (b) individuals hereditarily lacking in normal mental capacity, imbeciles and idiots; and (c) those lacking in moral or social endowment to such an extent as to constitute them abnormal members of society. The criminal classes are thus cited as defectives. In this latter sense the term includes those called degenerates. See DEGENERATION; also ATTENTION (defects of), HEARING, MEMORY, SPEECH, VISION, WILL. (J.J.)

Defective Syllogism: see SYLLOGISM.

Deferred (Instinct, Character, &c.): see INSTINCT, and ACQUIRED AND CONGENITAL CHARACTERS.

Deficient (in logic): see QUANTITY (logical).

Definite and Indefinite (in biology): see DETERMINATE (in biology).

Definite Term: see QUANTITY (logical).

Definition [Lat. de + finis, end]: Ger. Definition, Begriffsbestimmung; Fr. définition; Ital. definizione. The term definition is applied either to the process of fixing the limits of a notion, and so explaining it, or clearing it up; or to the proposition in which the result of the process is expressed, and there, again, it is sometimes confined to the predicate of the proposition.

The process starts from the content or comprehension of the thought to be defined, but would be inadequately expressed as an 'explication of the comprehension.' The explication comes about only by reference to the extensions, which are determined by the various marks making up the comprehension. Such reference, according to the logical doctrine, is said to be 'adequate,' if there be determined the genus, by preference the proximate genus, and the specific difference, the objects represented in the thought to be defined being thus distinguished from all others. The component parts of the definition, the genus and specific difference or species, may be, and have been, interpreted in the history of logic from a more objective, or from a more subjective, point of view.

The generic and specific marks constitute the essence (logical) of the definiendum, and there are thus excluded from the definition derivative and accidental marks. Individual objects and summa genera are logically indefinable. The test of a definition is the exact equivalence of the spheres of its subject and predicate. Definitions have been distinguished as (a) nominal, the explanation of the meaning of a word, and real, the explanation of the nature of the thing defined; (b) analytic, which starts with the notion as given, and synthetic, in which the notion is put together; of synthetic definitions, the most important is the genetic, the statement of the rule of operation by which the objects defined are represented as constructed, applicable in mathematics, and in practical sciences and arts; (c) rational, when the notion is determined from within, by thought, and empirical, when the notion is formed by selection from what is given in experience. These distinctions are not all happily expressed, nor free from difficulty. The term nominal definition, if retained at all, should be restricted to the explanations, given in any dictionary, of the accepted usage of language, explanations rendered necessary by the natural conditions of language. The thing defined is always that which is represented in our thought and sought to be expressed in our language; the mode of existence assigned to it is not determined by the definition, and falls outside of that. The other distinctions point to problems, partly of theoretical importance, partly of practice.

The doctrine of definition, beginning in the controversies between Plato and Antisthenes, received complete formulation in Aristotle, of whose logical analysis it is the culmination. The technical rules which he laid down have kept their place as the accepted, traditional logic, though the special interpretation of them by Aristotle has long been given up. In the scholastic disputes regarding universals, particularly in the school of Occam, there may be traced the beginnings of the larger questions regarding the function of definition in knowledge, the possibility and limits of it, which play the most important part in modern treatment of the subject. The Kantian philosophy, by its distinction of formal logic from theory of knowledge, separated the technique of definition as a formal process from the theoretical questions regarding the nature and scope of definition. From the empirical point of view, Mill emphasized the distinction between definitions which postulate, and those which do not postulate, the existence of objects corresponding to the definitions given.

Literature: for Aristotle's doctrine, see especially PRANTL, Gesch. d. Logik, i. 321-40. For the distinctions of kinds among definitions, see UEBERWEG, Logik, § 61. The modern problems are discussed in LOTZE, Logik, Bk. II chaps. i, ii; VENN, Empirical Logic, chap. xi; RICKERT, Lehre v. d. Definition (1888), and Die Grenzen der naturwiss. Begriffsbildung (1896). See also E. C. BENECKE, in Mind, vi. 530 ff. (R.A.)

Definitive: see METHOD (logical), WHOLE, and PROPOSITION.

Deformity (1) and (2) Deformation [Lat. de + forma, shape]: Ger. Deformität, Missgestalt; Fr. difformité, déformation; Ital. deformità, deformazione. (1) A lack of proper form or symmetry in the development of a part of the body; irregularity of features; disproportionate or unnatural deviation in structure from the usual. Somatic deformities are designated stigmata; see STIGMA.

(2) Artificial deformations are intentional distortions. The tendency to divert some portion of the human anatomy from its normal shape is very widespread. The custom at times acquires a special religious or ceremonial significance, but seems more frequently due to a crude aesthetic instinct. Flattening of the skull, constraining of the foot, piercing of the ears, nose, or lips to attach thereto ornaments of various types, separating and notching the teeth, twisting, curling, and knotting the hair, tattooing and painting the skin, illustrate various forms of development of this tendency. See Flower, Fashion in Deformity, 1881.

The term deformity is sometimes used figuratively to refer to mental defect or distortion, and is then equivalent to mental abnormality. (J.J.)

Literature: DELISLE, Contrib. à l'Étude des Déformations du Crâne (1858); LAGNEAU, in Gaz. heb. de Méd. (1879), 5, 6. (L.M.)

Degeneration [Lat. de + genus, race]: Ger. Entartung; Fr. dégénérescence; Ital. degenerazione. Decay or retrogression from the point of view of evolution. (J.M.B., G.F.S.)

While degeneration is a term applicable to biological processes in general, its psychological significance is limited to mental degeneration in man. As such it expresses a retrograde tendency in human evolution.

The conception of a class of degenerates was formed by Morel (1857). It includes a variety of types with the common factor of a nervous diathesis, and the presence of certain more or less definite abnormalities. In the lowest forms of degenerates hereditary influences are most prominent, and the defects of body and mind most marked; e.g. idiocy and cretinism complicated with such disorders as rachitis. The highest stage would be represented by persons of apparent normal intelligence, and even of an unusual development in certain directions. Such persons are apt to be enthusiastic and ambitious, with vivid imagination and impulsive temperaments; but their brilliancy of conception is not supported by industry and persistence. Moreover, they are apt to exhibit a want of balance in certain directions, which may develop into pronounced insanity. They form part of the borderland between sanity and insanity, in which marked eccentricity in certain directions is still entirely compatible with high ability, and the occupation of a worthy place in society. Between these extremes an indefinite number of types and classes may be interposed.

In the social sense, criminals of various grades -- the immoral and the outcast -- represent forms of degeneration. How far these can be described by characteristic physical symptoms is doubtful; but the occurrence of bodily abnormalities in such persons to a much larger extent than in normal individuals, though not in all cases (Magnan), has been clearly substantiated. Marked asymmetry, a misshapen skull, a peculiar form of ear, irregular teeth, rachitis, abnormal sexual development, are some of the characteristics noted as significant in this connection; while mentally, instability, violent excess, or again deficiency, of emotional sensibility, defective speech, mental dullness, or idiosyncrasies, may be mentioned. A most important factor is heredity; the families of the degenerate are apt to be afflicted with various forms of nervous disorder, such as alcoholism, insanity, idiocy, paralysis, or epilepsy accompanied often by immorality, and diseases of infancy both before and after birth. The frequency with which alcoholism and sexual excess appear in the history of degenerates is constantly noted; as is also the tendency of the degenerate to become the victim of such habits as indulgence in opium, hasheesh, and other psychical poisons. The doctrine of mental degeneration may readily be carried too far, but the term serves a useful function in describing a real but somewhat vague and heterogeneous class of abnormal individuals and tendencies.

Degenerative Insanity (Folie des dégénérés) refers to distinctive types of insanity to which degenerates are liable; such insanity is of strongly marked hereditary origin, and presents more or less morbid mental weakness, impulsiveness of will, and monomania. See DIATHESIS.

Literature: MOREL, Traité des Dégénérescences (1857), and Études cliniques; LEGRAIN, Du Délire chez les dégénérés (1886); MAUDSLEY, Pathol. of Mind (1880); MAGNAN, Des héréditaires dégénérés, in Recherches sur les Centres nerveux (2e série, 1893), 109-426; KOCH, Die psychopathischen Minderwerthigkeiten (1891); DALLEMAGNE, Dégénérés et Déséquilibrés (1894); FÉRÉ, Dégénérescence et Criminalité (1895), La Famille névropathique (2nd ed., 1898); TALBOT, Degeneracy (1898); A. MEYER, Signs of Degeneration, Amer. J. of Insan., v. 52, 344-63; PETERSON, N. Y. State Hosp. Bull. (1896); KRAUS, Amer. J. of Insan. (1898), iv. 655 ff.; SOLLIER, Psychol. de l'Idiot et de l'Imbécile; MEIGE, Les possédés noirs (1894). (J.J.)

Also KRAFFT-EBING, Lehrb. d. Psychiatrie; SCHÜLE, Lehrb. d. Psychiatrie (3rd ed. Klinische Psychiatrie); ARNDT, Lehrb. d. Psychiatrie, and Die Entartung (1896); MORSELLI-BALLET, Le Psicosi, in Trattato di Medicina di Charcot (trad. italiana); MAGNAN, Dégénérescence mentale, C. R. Soc. d. Biol., ix. (1894); LOMBROSO (and his pupils), opera omnia. (E.M.)

Degeneration (in biology). Retrogression from the more complex to the less complex, from a relatively elaborate and complete structure in earlier forms to a relatively simple or incomplete structure in later forms.

E. Ray Lankester (lecture on Degeneration before the British Association, 1879) says: 'It is clearly enough possible for a set of forces such as we sum up under the head "Natural Selection," so to act on the structures of an organism as to produce one of three results, namely these: to keep it in statu quo; to increase the complexity of its structure; or, lastly, to diminish the complexity of its structure. We have as possibilities either Balance, or Elaboration, or Degeneration.' Animals which acquire a sedentary and fixed mode of life (Ascidians, Cirripedes, &c.) and parasitic animals often undergo degeneration; the former losing locomotory and sensory organs, the latter often losing digestive organs as well (Tapeworms, &c.). The phylogenetic degeneration of the species (or organ) is often recapitulated in the ontogenetic degeneration of the individual, which in the course of its life-history is seen actually to pass from a higher to a lower type of structure (Ascidians).

Literature: ANTON DOHRN, Der Ursprung d. Wirbelthiere (1875); E. R. LANKESTER, Degeneration, in Adv. of Sci. (1890); Discourse before Brit. Assoc., Sheffield meeting (1879); and Degeneration (in Nature series); DEMOOR, MASSART, and VANDERVELDE, Evolution by Atrophy (Eng. trans., 1899). (C.LL.M. - E.S.G.)

Degeneration (nervous). Destruction or morbid alteration of the tissue of an organ as a result of injury or disease. Cf. ATROPHY, and APLASY.

Even normal functioning of the nervous tissue produces destructive alteration in the substance, and such changes carried beyond the point where they are readily restored may be termed morbid. Histological changes due to fatigue have been demonstrated (Hodge, Tuke, Mann, Lugaro, and others). See FATIGUE. The initial symptoms of degeneration may be active inflammations (neuritis, encephalitis, myelitis), or they may be of a more chronic and metabolic nature. In the central system circulatory changes (hyperaemia or vascular stasis) are among the earliest symptoms, though direct intoxications due to irritative poisons (alcohol or ptomaines) may also occur. The characteristic changes in nervous tissue proper are always accompanied by alterations in the sustentive (neuroglia) and nutritive apparatus.

Among all forms of nervous degeneration, that due to alcoholic poisoning is most instructive, as affording most conclusive evidence of the relation between structural and mental changes. The psychical symptoms are such as amnesia, diminished power of attention, insomnia, impairment of the will, and disturbances of the muscular and co-ordinating power, as well as a blunting of the moral perceptions. These are followed by hallucinations, delusions, and various chronic insanities. In many respects the disease is analogous to general paralysis of the insane. Corresponding to these functional changes are two sorts of structural alterations, viz.: (1) the impairment of the means of communication between neurocytes, showing itself in the destruction of the fine root-like processes of the dendrites, and afterwards in the formation of moniliform varicosities of the dendrites themselves as a result of decomposition; (2) changes in the cell-body itself, such as vacuolation, degeneration of protoplasm (pigmentation), and the results of imperfect or exaggerated nutrition. The capillaries are shrunken and irregular. See Plate A (DEGENERATION).

Experimental administration of alcohol to animals (Berkley) has resulted in changes entirely similar to those found in the human subject suffering from alcoholism. Pathological dementia results from the interruption of communication between cell and cell because of the loss of the gemmulae and tumefaction of the dendrites, so that co-ordination of the psychical centres becomes impossible. See PARALYSIS (general).

Degenerations due to peripheral lesions are well illustrated by the results of injury to the sense-organs. Thus, in case of destruction of the bulb of the eye, the anterior pair of the corpora quadrigemina are reduced in size, by reason of the degeneration of some nerve-cells and the atrophy of others, together with the disappearance of the fibres of the optic tracts and reticular substance. The external geniculatum is also greatly reduced in size, but this is due to the degeneration of fibres from the optic tract and the gelatinous substance, rather than of the neurocytes. There is a similar loss of substance in the pulvinar. The so-called Forel's commissure is the only one affected.

In congenital anophthalmia and atrophy of the bulb, a special layer of cells in the occipital cortex of the cerebrum is atrophied. These cells near the calcarine fissure, constituting the specific cortical centre for vision, are connected, via the optic radiations, with the geniculata.

Destruction of isolated areas in the cerebral cortex results not only in degeneration of the coronal fibres and pes pedunculi well into the cord, but in secondary degeneration of collaterals passing via the callosum to corresponding areas of the opposite side, and also of the arcuate or associational fibres of the corresponding hemispheres. In case of unilateral injury to the cortex, the callosal fibres degenerate as far as to the corresponding cortex of the opposite side. The number of degenerate fibres is proportional to the extent of the injury. In case of bilateral injury the amount of degeneration is greater. The associational (arcuate) fibres degenerate only on the side of the lesion. These phenomena explain the fact that the removal of a small cortical area diminishes the total psychical efficiency, for it is plain that the secondary degeneration must affect the larger circle of associations. Degeneration of nerve-fibres (neuritis) may result from peripheral irritation, or from disease of the cells of origin, whether gangliocytes in spinal ganglia, or neurocytes of the central system. In spite of great diversity in the details of such degeneration, all cases exhibit, according to Klippel, three stages: tumefaction of the myelin sheath, granular disintegration and fragmentation of the axis cylinder, with liquefaction of the myelin, and, finally, resorption of the whole. In acute cases the initial tumefaction is greater.

After complete seperation from the nervous centres, the peripheral part of a nerve suffers degeneration throughout its whole extent, even in those cases where continuity is eventually re-established. The changes in the latter case are as follows: (1) Segmentation of the myelin and axis cylinder at the intersegmental lines. (2) Proliferation and migration of the nuclei. (3) Fragmentation and resorption of myelin and axis cylinder. (4) Increase of protoplasm about the nuclei, which migrate to the axis of the nerve-tube; then follows the formation of a new axis cylinder. (5) Formation of a new sheath surrounding the embryonic fibre. (6) Union of the peripheral end with the stump, in which similar changes have taken place. (7) Formation of myelin -- a process which proceeds from the wound towards the distal end.

For details of Gudden's and Marchi's methods of employing experimental degeneration in research, see NEUROLOGY. (H.H.)

Literature: H. J. BERKLEY, Studies on the Lesions produced by the Action of certain Poisons on the Cortical Nerve Cell, (1) Alcohol, Brain, xviii (1895); E. BERGMANN, Ueber experimentelle aufsteigende Degeneration motorischer und sensibler Hirnnerven (Vienna, 1892); FOREL, Ueber das Verhältniss der experimentellen Atrophie und Degenerationsmethode zur Anatomie und Histologie des Centralnervensystems, Festschrift f. Nägeli und Kölliker (Zürich, 1891); v. GUDDEN, Experimentaluntersuchungen über das peripherische und centrale Nervensystem, Arch. f. Psychiatrie, ii (1870); G. C. HUBER, A Study of the Operative Treatment for Loss of Nerve Substance in Peripheral Nerves, J. of Morphol. (1895; accompanied by a good bibliography); HOWELL and HUBER, A Physiological, Histological, and Clinical Study of the Degeneration and Regeneration in Peripheral Nerve Fibres after Severance of their Connections with the Nerve Centres, J. of Physiol., xiii (1892), and xiv (1893); M. KLIPPEL, Comment débutent les dégénérescences spinales? Arch. de Névrol., 2e série, i (1896); STROEBE, Experimentelle Untersuchungen über die Degeneration und reparatorischen Vorgänge, in Ziegler's Beitr. z. pathol. Anat. u. z. allgem. Pathologie, xv (1894); G. B. VALENZA, Sui cambiamenti delle cellule nervose, in Mem. R. Accad. Sci., Napoli (1896); L. F. BARKER, The Nervous System and its Constituent Neurones, chap. xx (1899; full bibliography, with good digests of most recent work); F. NISSL, Ueber eine neue Untersuchungsmethode des Centralorgans speciell zur Feststellung der Localisation der Nervenzellen, Centralbl. f. Nervenh. u. Psychiat. (1894); H. STROEBE, Die allgemeine Histologie der degenerativen und regenerativen Processe im centralen und peripheren Nervensystem, nach den neuesten Forschungen. Zusammenfassendes Referat. Centralbl. f. allg. Pathol. u. pathol. Anat. (1895; digest of literature up to 1895); H. H. TOOTH, The Gulstonian Lectures on Secondary Degenerations of the Spinal Cord (London, 1889), and Brit. Med. J. (1889); A. WALLER, Experiments on the Section of the Glossopharyngeal and Hypoglossal Nerves of the Frog, and Observations of the Alterations produced thereby in the Structure of their primitive Fibres, London, Edinburgh, and Dublin Philos. Mag., 1850; also in Philos. Trans. (London, 1850), and in Edinburgh Med. and Surg. J. (1851). (H.H.)

Dégérando, Joseph Marie, Baron de. (1772-1842.) Born in Lyons, he was imprisoned by the republicans in 1794, during the siege of Lyons. He escaped to Switzerland and into the kingdom of Naples, returning to Paris in 1796. In 1797 he took part in the march against Italy.

Degree [Lat. de + gradus, step, through the Fr.]: Ger. Grad; Fr. degré; Ital. grado. See QUANTITY, INTENSITY (mental), and KIND AND DEGREE.

Degree of Consciousness: see SUBCONSCIOUS.

Deification: see APOTHEOSIS.

Deism [Lat. deus, God]: Ger. Deismus; Fr. déisme; Ital. deismo. The form of THEISM (q.v.) which separates God from the world, in the sense of denying that the concept of God includes in whole or part the concept of the world. (J.M.B.)

Deity: see GOD, THEISM, and RELIGION (psychology of).

Dejection [Lat. de + iacere, to cast or throw]: Ger. Niedergeschlagenheit; Fr. abattement; Ital. tristezza, mestizia. A state of mental depression or despondency. It is especially characteristic of weakened states of body and mind, such as neurasthenia; and is prominent most of all as a chronic characteristic of MELANCHOLIA (q.v.). The lowness of spirits in dejection, characteristic of individuals who are apt to take a gloomy view of the ordinary events of human life, led to the delineation of the melancholic temperament as one of the typical varieties. See TEMPERAMENT, and DEPRESSION. (J.J.)

Delamination [Lat. de + lamina, fold]: Ger. Spaltung; Fr. délamination; Ital. delaminazione. The splitting off of one cell-layer from another by means of cell-proliferation, e.g. of the mesoblast or of the PLANULA (q.v.). See also EMBRYO. (E.S.G.)

Delbrück, Johann Friedrich Ferdinand. (1772-1848.) He was born in Magdeburg, and studied in Halle under the Kantian Jacob and the anti-Kantian Eberhard. For several years he was a private tutor, then continued his studies, and in 1797 became an instructor in the gymnasium of the Grey Cloister in Berlin. In 1809 he became councillor to the East Prussian Government and professor of the theory, criticism, and literature of the fine arts; in 1816, councillor to the government and to the schools in Düsseldorf. He moved in 1818 to Bonn as professor of aesthetic literature and philosophy.

Deliberation [Lat. de + librare, to balance]: Ger. Ueberlegung; Fr. délibération; Ital. deliberazione. The comparison of alternative courses of action which precedes and issues in choice. The basis of comparison is to a very large extent the relation of the alternative courses and their consequences to the self as a whole. (G.F.S.- J.M.B.)

Delirium [Lat. delirium, madness, raving]: Ger. Delirium; Fr. délire; Ital. delirio. A temporary, disordered mental condition occurring particularly in fevers, and presenting excitement, wild, irregular, and incoherent thought, and a confused consciousness. There may also be hallucinations and illusions, ravings and violent actions. That form in which the patient is relatively inactive and maintains a low muttering is termed 'quiet' delirium, while that accompanied by violence and loud ravings is termed 'active' delirium. Although the symptoms presented are those typical of insanity, the two conditions are quite distinct; the insanity following a severe fever is also entirely distinct from the delirium of the fever itself.

Delirium is not confined to cases of fever, as other diseases may produce the cerebral conditions upon which the delirium depends. Particularly in affections of the brain and spinal cord, or their surrounding membranes, is delirium apt to be a prominent symptom. The nature of the mental wanderings is quite variable and individual, past experiences or fanciful ones occupying the patient's attention to the exclusion of the present. Although he can be momentarily aroused, and may respond to simple questions, he soon drifts back to the delirious state. From a clinical point of view delirium is characteristic of the special fevers (typhoid, scarlet fever, yellow fever, influenza, &c.); of inflammatory conditions of special organs (pneumonia, peritonitis, sunstroke, dysentery); of certain brain affections (meningitis, epilepsy, hydrophobia, lead poisoning, concussion); of such chronic diseases as Bright's disease; of the result of brain inanition (lack of food, exposure, loss of blood). In addition, the delirium caused by the action of drugs, or mental poisons, is especially significant, and of these the delirium of alcohol has been most extensively described. Opium, hasheesh, chloroform, ether, nitrous oxide, all produce more or less prolonged and characteristic forms of mental wanderings. See INTOXICATION, and PSYCHIC EFFECTS OF DRUGS. For Delirium Tremens, see ALCOHOLISM.

The term delirium is also used in reference to any marked and somewhat systematic delusion symptomatic of cases of insanity; thus the delirum of persecution, the delirium of grandeur; and it is similarly used with reference to such delusions in connection with the diseases of which they are symptomatic; as the delirium of epilepsy, of hysteria, of alcoholism, or mania sine delirio, and the like. See HALLUCINATION, and ILLUSION.

Literature: CHASLIN, La Confusion mentale, also Rêve et Delirium (1887); BIANCHI, La Frenosi sensoria (1895); MENDEL, art. Delirium in Eulenburg's Real-Encyk. der ges Heilkunde; textbooks of mental diseases. (J.J.)

Delusion [Lat. delusio, from de + ludere, to play]: Ger. Wahnvorstellung; Fr. illusion, idée fausse ou fixe; Ital. illusione (psichica), delirio. A false belief or perception determined by belief; typically it is of a somewhat persistent nature, and involves more or less elaborate reasoning processes.

It differs from an illusion (when these words are precisely used), in that the illusion is a direct mental construction in which the element of logical inference is slight; and from an hallucination, in that the hallucination is a false perception arising from within, largely independent of an external stimulus. See HALLUCINATION, and ILLUSION. (J.J. - J.M.B.)

When used popularly, delusion may refer to a false belief, due to ignorance, imperfect education, or bias; when used in reference to abnormal mental states, a delusion is due to a perverted or morbid mental action which prevents the subject from realizing the falsity of his belief, either by the evidence of his senses or otherwise. Such fixed and elaborate delusions are almost always evidences of insanity. In rather rare cases they constitute the sole disorder, which is then termed delusional insanity. When limited, as they usually are, to a few topics, they form the monomanias which contribute so largely to the popular conception of insanity, and give distinctiveness and individuality to the inmates of insane asylums. PARANOIA (q.v.) is an allied condition, of which delusion is the most characteristic symptom.

The types and varieties of delusion are almost endless in scope. They may be distinguished according to their mode of affecting the subject as elevating or exciting, or as depressing, or again as modifying the personality. Another classification is based upon the form of the delusion, whether of grandeur, of suspicion, of persecution, of unseen agency, &c. Clouston gives a list of nearly a hundred special delusions, such as the unreasonable belief in being poisoned, defrauded, of being pregnant, having no body or no stomach, that it is wrong to take food, of being in relation with the devil, of letters being written about one, of having committed murder or other crimes, of being called names, of being a king, being God or Christ, &c. Many of these delusions become systematized and enlarged, and may involve hallucinations and illusions; while other remain purely in the delusional realm of false beliefs. For further details see HALLUCINATION, ILLUSION, INSANITY AND SANITY, MANIA, MELANCHOLIA, and DEMENTIA.

Literature: EMMINGHAUS, Allgemein. Psychopath.; MORSELLI, Semej. malat. ment., ii; FRIEDMANN, Ueber den Wahn (1894); KRAEPELIN, Psychiatrie, i. 159-77; DE JONG, La Psychologie des Idées fausses des Aliénés, Verh. d. 3ten int. Congr. f. Psychol., Munich (1896); KOCH, Die überwertigen Ideen, Centralb. f. Nervenh., xix; HIRSCH, Physical Mechanism of Delusion, J. of Nerv. and Ment. Dis. (1898), 157 ff. (J.J.)

Demand [Lat. de + mandare, to entrust]: Ger. Nachfrage; Fr. demande; Ital. domanda. (1) The quantity of a given commodity, which the buyers in a given market are ready to purchase at a given price. (2) The rate at which buyers are ready to carry off the commodity at a given price, i.e. the quantity they will take per unit of time. (3) The quantity of purchasing power offered, at a given price relation, in exchange for the article demanded.

Demand is a quantity; desire, a feeling. This radical difference was not at first perceived. Smith distinguished absolute demand (quantity desired) from effectual demand (quantity which the buyer was both willing and able to purchase at the natural price). Ricardo, Malthus, and Mill gradually advanced to the conception given in (1): a sliding scale, or series of relations between quantity and price. This idea was given exactitude by Cournot and Dupuit.

The development of the mathematical theory of consumption has led most modern writers to substitute the conception (2), of a rate of demand for a pure quantity, and to make the problem of market price a kinetic rather than a static one. Cf. SUPPLY AND DEMAND.

Malthus noted two senses of demand, corresponding roughly to the distinction between (1) and (3). The last named meaning was emphasized by Walras and by Cairnes. Marshall says that there is no fundamental difference between (1) and (3), because, when the price is introduced, the two expressions reduce  to the same pecuniary value; but he fails to see that when we take demand as a series of relations, the price is usually an unknown quantity to be determined; and that Cairnes' method of determination differs fundamentally from Mill's. (A.T.H.)

Dementia [Lat. de + mens, mind]: Ger. Schwachsinn; Fr. démence; Ital. demenza. One of the main types of mental disorder, characterized by acquired (not congenital) enfeeblement of mental power.

Persons so afflicted are sometimes called 'dements.'

There may be no excitement, depression, or aberration, but only a more or less pronounced inactivity, and loss of mental receptivity and capacity. It is impossible to fix any particular degree of mental impairment as constituting dementia, as it may vary from a slight failing of the mental powers to a condition of utter helplessness of body and mind. It has been characterized as 'a general weakening of the mental power, comprising usually a lack of reasoning capacity, a diminution of feeling, a lessened volitional and inhibitory power, a failure of memory, and a want of attention, interest, and curiosity.' Lack of initiative is marked; even when once aroused, the mental powers are fairly normal.

The commonly described forms of dementia are the following: (1) Primary dementia is really a form of STUPOR (q.v.), which many prefer to describe under this head or with katatonia. It usually comes on during adolescence as a form of extreme inactivity and abeyance of mental faculties, and may be only temporary. It is akin to deep amentia.

Several writers (Kraepelin. Psychiatrie, 6th ed., ii. 137-214; and Zeitsch. f. Psychol., 56, 254; Christian, Ann. Méd. - Psychol., 1898, 1899) describe as dementia praecoxi a primary tendency to decline into dementia, with marked apathy, automatisms, recurring short periods of depression and excitement, &c., but without the concomitant symptoms with which such traits are connected in mania, melancholia, or paranoia.

(2) Secondary dementia, the ordinary form, is often termed sequential or terminal dementia, as it represents the final stages of other forms of insanity, mania, melancholia, &c. Here again degrees are important, and depend largely on the duration, nature, and severity of the former insanities. Many dements are practically reduced to an animal existence, losing all sensibility and refinement, becoming unclean in habit and idiotic in appearance. They seem almost dead to their own past, no longer recognize their friends, and if unaided by those about them would quickly perish. Less severe cases are more active physically, are able to occupy themselves with simple household duties, and frequently live long, dying of other causes than the brain degeneration. In some cases dements are liable to sudden outbursts of excitement and violence; and destructive tendencies are common amongst them. The anatomical changes are very obscure, perhaps more marked in the internal organs than in the nervous system. Kraepelin holds that the cases of secondary dementia present not a dementia following mania or melancholia, but from the start are characteristic processes of deterioration. See PSYCHOSES.

(3) Senile dementia is an exaggerated form of normal senescence, in which the mental enfeeblement proceeds more rapidly and to a greater extent than usual. Bodily decrepitude accompanies the loss of memory and other faculties. In certain cases hallucinations and delusions occur. Distinct pathological changes in the brain and its membranes have been substantiated.

(4) Paralytic dementia is a term which is used as synonymous with the dementia or final stage of general PARALYSIS (q.v.). In addition, some writers distinguish alcoholic or drug dementia, and organic dementia, which results from gross brain disease.

Literature: CLOUSTON, Ment. Diseases (4th ed., 1896), lects. vii, viii, and x; RIEGER, Beschreibung der Intelligenzstörungen (1888); ZIEHEN, Allgem. Path. des Intelligenzdefects, in Lubasch and Ostertag's Ergebnisse der Allg. Pathol. (1899); all systematic works on mental diseases. (J.J.)

Demerit [Lat. de + merere, to deserve]: Ger. Unverdienst; Fr. démérite; Ital. demerito. (1) Ethical: see MERIT.

(2) Theological: the condition of inability on man's part to achieve more than a certain modicum of righteousness, and absence of power to remain on a moral level satisfying to God. It is a consequence of the view of human nature issuing from the dogma of original sin. (R.M.W.)

Demesne [OF. demaine, possession]: Ger. Domäne; Fr. domaine; Ital. dominio. That portion of a mediaeval manor which the lord retained in his own passion and cultivated by means of his serfs, or that portion of a mediaeval kingdom of which the king remained immediate lord. (F.C.M.)

Demiurge: see GNOSTICISM, and SOCRATICS (Plato).

Democracy [Gr. dhmoV, people, + kratoV, power]: Ger. Demokratie; Fr. démocratie; Ital. democrazia. By derivation simply 'rule of the people.' Specifically: (1) A form of government in which the control lies with the mass of the people, without respect of fortune. (2) Sometimes loosely: the great mass of the people themselves. (3) Sometimes in the United States: the Demoncratic party, supposed to represent the rights of the people in some peculiar sense.

The typical democracies are: in ancient times the Greek (Athens), in mediaeval the Italian (Florence), in modern Switzerland and the United States.

Plato unhistorically represents democracy as growing out of oligarchy (plutocracy) and passing into tyranny (Republic, viii). Aristotle agrees with Plato that it is the rule of the poor (Pol., III. v), but sees more virtue in it than Plato. The presence of slavery in ancient democracies detracts from their democratic character. The device of representation enables modern democracies to embrace much larger bodies of men than the ancient, though Rousseau counts democracy best suited for small states, monarchy for large (Contrat Social, iii). Lewis points out that the division of governments into monarchies, oligarchies, and democracies is as old as Herodotus Bk. III). It probably became current in his time (5th century B.C.), though he represents it as older.(J.B.)

Literature: for the aspects of modern democracy see MONTESQUIEU, ROUSSEAU, and DE TOCQUEVILLE. Cf. CORNEWALL LEWIS, Political Terms, chap. ix, Democracy, and the authors there quoted; also chap. v, Sovereignty.

Democritus. (cir. 460-cir. 357 B.C.) A Greek philosopher, born at Abdera, Thrace. Called 'The Laughing Philosopher,' for his cheerful disposition. He was rich by inheritance, and devoted himself to travel and learning. He was probably the greatest of the followers of Leucippus. See PRE-SOCRATIC PHILOSOPHY (Atomists).

Demography [Gr. dhmoV, people, + grafein, to write]: Ger. Demographie; Fr. démographie; Ital. demografia. The statistical description of human populations in their physical, rather than in their social and moral aspects.

The term is of recent origin. 'Il y a toutefois une étude qui constitue assurément une science et qui est si étroitement liée avec la statistique, qu'on l'a confondue souvent avec elle; c'est la démographie. . . . La démogaphie est la science de la population; elle en constate l'état, elle en étudie les mouvements, principalement dans la naissance, le mariage, la mort et dans les migrations, et elle s'efforce de parvenir jusqu'à la connaissance des lois qui la régissent' (E. Levasseur, La Population Française, i. 18). (F.H.G.)

Demon [Gr. daimwn, a god, an evil spirit]: Ger. Dämon; Fr. démon, diable; Ital. demonio, diavolo. Supernatural beings less than divine, which may be (1) either good or bad, or (2) only bad.

Philosophically viewed, demons are connected (1) with man's tendency to regard unknown, or imperfectly known, phenomena from an anthropomorphic or anthropopathic standpoint. This accounts for the wide differences in the connotation of the term to be found, as matter of history, in various civilizations. The personification of cosmic phenomena (animism) must be cited as the origin of all such conceptions. Viewed in this, the more general, way, demons are supernatural beings who may be good or bad. The conception is preserved in our modern phrase 'good or evil genius.' (2) More specifically, demons are directly connected with man's ideas of the origin of evil and of the causes of misfortune. They are external causes, causes contrasted with those to be found in man's own spirit or in his bodily weaknesses. In this regard, they are specially characterized by the fact that, unlike wood-sprites fairies, and similar beings, they interest themselves in human affairs. They cannot be treated as non-moral or unmoral. They are baleful agencies as a rule. Although, according to the older views, their activity may be for good (as often in the Arabian Nights), since the Christian era they have been deemed essentially evil, in contrast to good spirits -- angels. This alteration of standpoint is due to the dogma of the Fall; and although distinct traces of its influence are to be found in pre-Christian culture (e.g. Isa. xiv. 12 f.), the almost exclusive stress laid upon this idea by the Christian consciousness is absent. See DEMONOLOGY (also for Literature). (R.M.W.)

Demonolatry [Gr. daimwn + latreia, service]: Ger. Dämonolatrie; Fr. démonolatrie; Ital. demonolatria. The worship of spirits -- good or, as is more usual, evil.

Generally it may be said that, till distinctively theological conceptions have matured -- and this is specially true of Christian theology -- no deliberate choice is made of an evil being as an object of worship. Hence, demonolatry is usually a simple propitiation of spirits that might do harm were they to be slighted. MAGIC (q.v.), in its various forms, may be taken as expressive of this propitiation. Worship, in the sense of adoration, plays a minor part, and, when it does take place, incantation rather than prayer figures prominently. See DEMONOLOGY (also for Literature). (R.M.W.)

Demonology [Gr. daimwn, a demon, + logoV, discourse]: Ger. Dämonologie; Fr. démonologie; Ital. demonologia. In the most general anthropological sense, demonology treats of systems of beings intermediate in rank between gods and men.

Under the dominance of Christian influence the demons became the spirits of evil, while the angels became the spirits of good. Like all such doctrines, the conception of the demon has a long history and development, in which are reflected the culture stages of the believers in the demon's acts and powers. In savage peoples the demon is hardly more than a human soul under new conditions of existence; the doctrine thus becomes closely related to the general views of the nature of the soul and of life after death (see ANIMISM). The most influential field of the demons, whether viewed as the ghosts of the dead or as separate and superhuman beings, was in the production of disease; and to a lesser extent they were summoned to account for the failure of crops, and the various good and ill fortunes of a primitive existence. The patient was seized or possessed by the demon (hence the term epilepsy), and in case of nervous attacks (trance, mania, epilepsy, &c.) the foreign spirit might be heard speaking through the mouth of the possessed body. The specific nature of the belief in the demon is usually well shown by the arts practised to banish or to exorcize it (see EXORCISM), such practices being frequently of the nature of magical or religious charms. Dreams and nightmares were also explained as the result of demon possession. In more developed civilizations the demon notions change their character, and are strongly influenced by the prevalent religious systems and observances. But practices closely akin to those derived from immediate belief in demon possession remain as survivals to the present day. The detailed history of the beliefs in demons, with their elaboration into hierarchies with specific and individual functions, forms a most important chapter in the history of the development of religion. See also DEMONOMANIA, and WITCHCRAFT.

Literature: art. Demonology in Encyc. Brit. (9th ed.), and references there given; NEVIUS, Demon Possession (1895); A. D. WHITE, Hist. of the Warfare of Science with Theology, chaps. xv, xvi; LEHMANN, Aberglaube u. Zauberei (1898); also references under ANIMISM and EXORCISM. (J.J.)

Demonology (religious). The department of science and history of religions which deals with the belief in demons, taking this phrase in its widest acceptation. The main problems are: (1) to give an authentic account of demons in all the phases of religious culture, from the lowest nature-religions to Christianity; (2) to show how the definite demon-system of one religion or people (e.g. Persia, Babylonia-Assyria) has influenced the development of another (e.g. the Jews after the Exile). Philosophically, the problem is to determine how, at different times and under various conditions, men have conceived of their relation to demons, especially as regards the ethical implications of this relationship.

Literature: ROSKOFF, Gesch. d. Teufels; TYLOR, Primitive Culture; H. SPENCER, Princ. of Sociol., i; A. BASTIAN, Der Mensch in d. Gesch., and Beitr. z. vergleichenden Psychol.; WELCKER, Griech. Götterlehre, i. 731 f.; DOUGHTY, Arabia Deserta; KING, Babylonian Magic and Sorcery; TIELE, Babylon. - Assyr. Gesch., 548 f.; BAUDISSIN, Stud. z. Semit. Religionsgesch.; ROBERTSON SMITH, Religion of the Semites; WEBER and SCHNEDERMANN, Syst. d. altsynagog. Palästin. Theol.; EISENMENGER, Entdecktes Judenthum; EVERLING, Die Paulinische Angel. u. Dämonologie; CONYBEARE, in Jewish Quart. Rev. (1896); art. Exorcismus in Herzog's Real-Encyc.; CONWAY, Demonology and Devil Lore; PFLEIDERER, Philos. of Religion (Eng. trans.), iii. 307 f. See DEVIL. (R.M.W.)

Demonomania or Demon Possession [Gr. daimwn, a demon, + mania, madness]: Ger. Dämonomanie, Besessenheit; Fr. démonomanie; Ital. demonomania. Demonomania is a morbid mental condition, in which the patient believes himself, more usually herself, possessed by a demon. The term demon possession may be applied either to this condition or to the prevalent belief that certain forms of disease or manifestations are caused by demons. Possession and spirit possession are also used, to give a wider field for interpretation.

The condition may be considered either as a type of insanity, or in its historical aspects. As the former it is often akin to a religious melancholia, the patient believing himself eternally damned, suffering from agonies of self-accusation, and exhibiting many of the characteristics of melancholiacs. Another type of demonomania is the hysterical one, characterized by convulsions, and thus giving rise to the term Convulsionaires. Such demonomaniacs are subject to attacks of violence and fury, accompanied by starts and choreic jerks, and loud shouting, in which the central idea of possession by a demon is prominent. In extreme cases this crisis, which lasts from ten minutes to half an hour, may be accompanied by assaults on the bystanders, destruction of property, beating of their own bodies. A very constant symptom of the attack is anaesthesia. Ecstasy, catalepsy, and somnambulism may be noted; and most characteristic is the tendency of such attacks to be contagious and lead to epidemics (see CONTAGION). A person so affected may be termed a demoniac or demonomaniac. It is especially significant as a symptom of the delirium of degeneracy.

On the historic side, demon possession is important as a stage in the development of medical theory of disease, and as suggesting a rational explanation in terms of modern psychiatry of the actions and influences of abnormal individuals in former ages. In this connection it has an equal significance for the history of religion. Cf. DEMONOLOGY (with literature there cited). (J.J.)

Literature: V. MAGNAN, Leçons cliniques (1893, 2e série 1897); and Recherches sur les centres nerveux (2e série 1893); MAGNAN and LEGRAIN, Les Dégénérés; MAGNAN and SERIEUX, Le Délire chronique; MICHLA, Nouv. Dict. de Méd. (1872), sub verbo; BONFIGLI, Riv. sper. fren., 1893; also the titles cited under CATALEPSY (L.M.)

Demonstration [Lat. de + monstrare, to show]: Ger. Demonstration, Beweisführung durch Schlussfolgerung; Fr. démonstration; Ital. dimostrazione. A reasoning in which the conclusion has at once the logical necessity which expresses its relation to the premises as grounds from which it follows, and the material necessity which expresses the assumption that the premises are themselves judgments of objective worth. All demonstration therefore implies that the premises from which the conclusion proceeds are ultimate truths, the validity of which admits of no question, and the certainty of which requires no evidence. The problems which such a description of demonstration suggests -- viz. (1) what is the kind of certainty attaching to judgments of objective worth? (2) within what spheres are such judgments possible? (3) on what does the possibility of such judgments rest? -- from the main topic of the theory of knowledge.

Demonstration is the latinized equivalent for Aristotle's term apodeixiV, and all definitions of it are more or less transcripts of his definition of apodeixiV (Anal. Post., i. 2). The term demonstration does not appear to have become the current, accepted equivalent till the period of the Arabic writers on logic, who translated apodeixiV by it. The earlier Latin use, as in Boethius, does not go beyond the etymological sense, of showing, bringing before the mind as if pointed to, which the term still retains even in its specialized acceptation. For it is the peculiarity of demonstration that it claims for the conclusion reached by a mediating process the same simple absolute certainty that we incline to allow, without question, to the direct apprehension of a fact. The fundamental problems regarding demonstration begin in English philosophy with Locke's assignment of relations among abstract ideas to demonstration, and contrast of those with propositions about matters of fact. Locke's view was developed further by Hume, and Hume's mode of treatment reappears in J. S. Mill (Logic, Bk. II. chaps. v-vii); cf. excellent remarks in D. Stewart (Philos. of Hum. Mind, Pt. II. chaps. iv, v). The critical philosophy has brought the problem to the issue as to the exact character of judgments that are synthetic and at the same time claim to be self-evident. See Kant, Critique of Pure Reason, Doctrine of Method, chap. i.

Literature: MANSEL, Limits of Demonstrative Science, in Letters, &c., 79 ff.; LOTZE, Logik, Bk. III. chap. v; SPENCER, First Principles, Pt. II. chap. ii; KROMANN, Unsere Naturerkenntniss; JAMES, Princ. of Psychol., chap. xxviii; DELBOEUF, Essai de Log. scient. (R.A.)

Demonstrative: see DEMONSTRATION, and REASONING.

Demoralization [Lat. de + moralis, moral]: Ger. Demoralisation; Fr. démoralisation; Ital. demoralizzazione. The introduction of moral or mental disorder. See DISORDER (moral), and ORDER (moral). (J.M.B.)

De Morgan, Augustus. (1806-71.) An English mathematician, who contributed much to formal logic. He was professor of mathematics in University College, London.

Dendrite [Gr. dendrithV]: Ger. Dendrit, Protoplasmafortsätze; Fr. dendrite; Ital. dendrito. One of the protoplasmic or cellipetal processes of a neurocyte or nerve-cell. See NEUROCYTE (or NEURONE).

The term protoplasmic process, still in use, implies the older view that these projections served a nutritive function solely. It seems to be abundantly indicated that they receive nervous stimuli. The dendrite is commonly provided with root-like gemmulae, which are said to be the first to be attacked in nervous degeneration. (H.H.)

Denomination (logical) [Lat. de + nomen, a name]: Ger. Benennung; Fr. dénomination; Ital. denominazione. Denomination, in the scholastic logic, was a characteristic of terms, dependent on the relation of primary and derivative, especially in the case of an abstract term and the derived concrete.

Iustus, albus, e.g., were said to be predicated denominatively, because they referred to the possession of certain marks, i.e. were derived from iustitia, albitudo, possessed by the subject. In this sense the term is no longer used. Nor has the only other employment of it, as the process by which a name is selected for the common attributes recognized in the process of generalization and imposed on the class, acquired general acceptance. Cf. Thomson, Laws of Thought, § 48. (R.A.)

Denominative: see NAME AND NAMING, and TERM.

Denotation [Lat. de + notare]: Ger. Bezeichnung; Fr. dénotation; Ital. notazione (on the foreign equivalents compare CONNOTATION). Denotation, as a technical term, is used in a narrower and in a wider sense. In the former it is expressly relative to CONNOTATION (q.v.), and applicable within the range of the distinction between concretes and their attributes. In this sense it indicates one function of every concrete general name, that whereby a number of individuals (things, persons, cases) are marked off as possessing the attributes which constitute the meaning of the name. From this point of view, denotation might be said to march with connotation up to and exclusive of the lower limit (the proper name) and of the higher limit (the abstract term). In the wider sense, which connects with the vague untechnical use of the word 'denote,' denotation would include also the function of names where the connotative reference is absent, and from this point of view the proper name and the strictly abstract term would be said to have denotation; the one denoting a concrete individual without reference to attributes possessed in common with others; the second denoting an attribute or group of attributes conceived in abstracto, i.e. without reference to concrete exemplification of them.

Historically, the technical use of denotation seems to be due to J. S. Mill, whose account has been followed in the definition given. The obscurity which results from the conjunction of a wider and a narrower sense of the term has given rise to a number of disputes, of no great importance. Denotation, in the narrower sense, is equivalent to logical EXTENSION (q.v.).

Literature: MILL, Logic, Bk. I. chap. ii; KEYNES, Formal Logic, Pt. I. chap. iii. (R.A.)

Density [Lat. densitas, thickness]: Ger. Dichtigheit; Fr. densité; Ital. densità. Familiarly, specific gravity. The quantity of matter, or mass, contained in unit volume of a body.

At any given place it is proportional to the ratio of the weight of a body to its volume, whence the old term specific gravity. The concept being independent of gravity, the term density is now that most used in physics. (S.N.)

Denumeral: see MULTITUDE.

Deontology [Gr. deonta, duties, + logoV, discourse]: Ger. Pflichtenlehre; Fr. déontologie, théorie des devoirs; Ital. dottrina dei doveri, deontologia. The theory of duty or obligation.

The term is sometimes used to describe ethical science. It indicates a view of ethics in which the conception of duty, rather than those of right, virtue, or goodness, is made fundamental in morality.

The term was used by Bentham as the title of one of his late works (first published by Bowring), although, on his view, as expressed in the Principles of Morals and Legislation, duty was a social or political conception, and room was not found for it in the region of 'private ethics.' (W.R.S.)

Dependence [Lat. de + pendere, to hang]: for foreign equivalents see INDEPENDENCE. Any relation of CONDITION (q.v.), or CAUSE (q.v.).

Dependence (consciousness of): see RELIGION (psychology of).

Dependence and Dependent (in logic): see RELATION.

Depreciation [Lat. depretiare, to depreciate]: Ger. Entwertung; Fr. dépréciation; Ital. deprezzamento. Loss of value: commonly applied to the currency only, in which case it means decrease in the quantity of commodities which a monetary unit will purchase.

The cause of depreciation may be either increase in the supply of money or diminution in the demand for money. The former is the more common. Among its most frequent causes are (1) increased production of the precious metals; (2) emission of paper money by governments. The chief causes of diminution in demand are (1) substitution of credit for money as a means of exchange; (2) distrust in the money authorized by the government, and substitution of some other basis of contract.

Depreciation manifests itself by a rise in prices; see INDEX NUMBER. This results in a loss to creditors and to those who have fixed incomes, and in gain to debtors and those who have contracts to pay fixed sums. For the former can buy less goods with the money they receive, while the latter can discharge their debts or fulfil their contracts with fewer commodities or less labour.

The opposite of depreciation, both in its causes and effects, is appreciation. (A.T.H.)

Depression [Lat. de + premere, to press]: Ger. Traurigkeit, Depression; Fr. dépression; Ital. depressione. A condition characterized by a sinking of spirits, lack of courage or initiative, and tendency to gloomy thoughts.

The symptom occurs in weakened conditions of the nervous system, such as neurasthenia, and is especially characteristic of melancholia. Dejection and depression are practically used synonymously; depression refers more definitely to the lowered vitality of physical and mental life, dejection to the despondency of the mental mood. See DEJECTION, and MELANCHOLIA. (J.J.)

De primo ad ultimo: see SORITES.

Depth (in logic). A term generally used as synonymous with COMPREHENSION (q.v.). Cf. Hamilton, Logic, i. 141. (R.A.)

Depth or Distance, Visual (perception of): Ger. optische Wahrnehmung der Tiefe; Fr. perception visuelle de la profondeur (du relief, de la distance -- L.M.); Ital. percezione della profondità (distanza). The visual perception of depth or of the third dimension may be either a monocular or a binocular perception. (1) Monocularly, the perception may be mediated by degree of accommodation, by dispersion images, or by the apparent motion of one object in front of another which is caused by movements of the head or of the body. Mathematical perspective, aërial perspective, overlapping of figures, cross shadows, are all monocular criteria also, though secondary. No one of these criteria is very reliable; so that (except in so far as it is aided by associated binocular habits or ideas) monocular vision is characterized by lack of fine discrimination of depth. (E.B.T. - E.C.S. - C.L.F.)

(2) Binocularly, the perception may be mediated by disparate images or by the movements of convergence and accommodation. The part played by the two possible factors in actual perception is still a matter of dispute (see Hillebrand, Zeitsch. f. Psychol., xvi. 71; Arrer, Philos. Stud., xiii. 116, 222, and references there quoted). Secondary criteria, in binocular perception, are the relative clearness of the object fixated, its size, the distribution of light and shade upon it, the number of objects lying between it and the body of the observing subject, its relative speed of movement across the field of vision, &c. Cf. ABERRATION (chromatic). (E.B.T.)

Literature: Physiological Psychologies of WUNDT and LADD; Psychologies of JAMES (especially) and KÜLPE; for references to literature see also Psychologies of DEWEY, LADD, and BALDWIN; recent résumé by BOURDON, Année Psychol., iv. 390 ff. (J.M.B.- L.M.)