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The expression "heredity of acquired characters" generally refers to the transmission to descendants of modifications taking [[place ]] in the course of the [[individual ]] [[life ]] of a forebear, such transmission [[being ]] possible by virtue of these modifications being integrated into the forebear's genotype. Such modifications may be morphological, functional, or even behavioral (acquired through learning). This [[idea]], which was central to the evolutionism of Jean-Baptiste Lamarck, was later very largely rejected. [[Freud ]] nevertheless accorded it a non-negligible [[role ]] in some of his [[theoretical ]] views.

We have to bear in [[mind ]] that [[psychiatry ]] and [[psychology ]] at the end of the nineteenth century were very strongly marked by the idea that individual characteristics were essentially determined by hereditary data (in the genetic [[sense]]), whether in reference to normal or pathological [[development]], including [[mental ]] pathologies. It must also be said that in this [[domain ]] the [[theory ]] of degeneration was well established.

It is not surprising that Freud initially stood by the theory. In 1888 he wrote, in agreement with Jean Martin Charcot, that "the aetiology of the status hystericus is to be entirely looked for in the heredity" (1888b). However, he made a clear [[distinction ]] over the following years between the inherited "constitutional" causes that provide the individual's base [[psychic ]] terrain, and the "occasional causes," principally the vicissitudes of [[sexual ]] life, which alone could explain the [[appearance ]] and [[form ]] of the mental [[pathology]]. Publishing his [[translation ]] of Charcot's Leçons du mardi (Tuesday lectures), he went so far as to contradict him by [[writing ]] that "the most frequent [[cause ]] of [[agoraphobia]], as well as the [[other ]] phobias, does not reside in heredity but in the anomalies of [[sexual life]]" (1892-94a).

In Studies on [[Hysteria ]] (1895d) he actively criticized recourse to the [[notion ]] of degeneration as an explanation of [[hysterical ]] phenomena, and restated the complementary [[nature ]] of constitutional and accidental causes. He never departed from this [[position]], which he stated clearly in the manuscripts he addressed to Wilhelm Fleiss (Ms B, 1950a), then repeated in his article in [[French ]] on Heredity and the Aetiology of the [[Neuroses ]] (1896a), and each [[time ]] over the following years that he discussed the problem of the "[[choice ]] of [[neurosis]]"—the determination of a [[subject]]'s evolution toward hysteria or [[phobia]].

The problem took on a greater [[dimension ]] when Freud undertook to answer the question that cannot fail to rise in such a perspective: where do the "constitutional causes" themselves come from? He answered with a [[thesis ]] inspired by Charles [[Darwin]], and even more so by Ernst Haeckel, that found its most [[complete ]] formulation in [[Totem ]] and [[Taboo ]] (1912-13a): major events in the [[prehistory ]] of humanity mark all its later development and fashion the individual development of each [[child]]. This recourse to "phylogenesis" was coupled with two postulates: the first borrowed from Lamarck (transmission of acquired characters), the second from Haeckel (ontogenesis recapitulates phylogenesis). He focused on the hereditary transmission of general [[developmental ]] factors and psychic function, remaining more discreet on the subject of differential factors.

These [[Freudian ]] theses have been vigorously criticized, particularly their Lamarckian aspect which seems to have been eliminated by the victory of neo-[[Darwinism ]] and modern genetics. Contemporary [[work ]] in molecular genetics and population genetics seems to [[suggest ]] new ways of formulating the question of psychic heredity (Chiland C., Roubertoux P., 1975-1976).

See also: [[Constitution]]; [[Cultural ]] transmission; [[Identification ]] [[fantasies]]; [[Instinct]]; [[Intergenerational]]; Phylogenesis; Phylogenetic [[Fantasy]], A: [[Overview ]] of the [[Transference ]] Neuroses; Prehistory; [[Thalassa. A Theory of Genitality]].[[Bibliography]]