There are people whose desires behave in every way like sexual ones, but who at the same time entirely disregard the sexual organs or their normal use; people of this kind are known as "perverts."

Perversion was defined by Freud as any form of sexual behaviour which deviates from the norm of heterosexual genital intercourse.

However, this defmition is problematized by Freud's own notions of the polymorphous perversity of all human sexuality, which is characterized by the absence of any pregiven natural order.

Lacan overcomes this impasse in Freudian theory by defining perversion not as a form of behaviour but as a clinical structure.

"What is perversion? It is not simply an aberration in relation to social criteria, an anomaly contrary to good morals, although this register is not absent, nor is it an atypicality according to natural criteria, namely that it more or less derogates from the reproductive finality of the sexual union. It is something else in its very structure."

The distinction between perverse acts and the perverse structure implies that, while there are certain sexual acts which are closely associated with perverse structures, it is also possible that such acts may be engaged in by non-perverse subjects, and equally possible that a perverse subject may never actually engage in such acts.

It also implies a universalist position; while social disapproval and the infraction of "good morals" may be what determines whether a particular act is perverse or not, this is not the essence of the perverse structure.

A perverse structure remains perverse even when the acts associated with it are socially approved. Moreover, in Lacan's formulation, it is the neurotic subject who is in conflict with the Name-of-the-Father, in other words, with Law as such. The perverse subject, on the other hand, 'knows very well' the letter of the Law--in other words, knows what the Other desires. The perverse structure follows the Law to the letter, follows the "No" of the Father--the dictum not to enjoy. According to Jean Clavreul, " As far as the pervert is concerned, this conflict [between desire and Law] is resolved by making desire the law of his acts."

Hence Lacan regards homosexuality as a perversion even when practiced in Ancient Greece, where it was widely tolerated. This is not because homosexuality or any other form of sexuality is naturally perverse; on the contrary, the perverse nature of homosexuality is entirely a question of its infringement of the normative requirements of the Oedipus complex.

Thus Lacan criticizes Freud for forgetting at times that the importance of heterosexuality in the Oedipal myth is a question of norms and not of nature. The analyst's neutrality forbids him from taking sides with these norms; rather than defending such norms or attacking them, the analyst seeks merely to expose their incidence in the subject's history.

There are two main ways in which Lacan characterizes the perverse structure.

Perversion is distinguished from the other clinical structures by the operation of disavowal.

The pervert disavows castration; he perceives that the mother lacks the phallus, and at the same time refuses to accept the reality of this traumatic perception.

This is most evident in fetishism (the "perversion of perversions") where the fetish is a symbolic substitute for the mother's missing phallus. One can also formulate the fetish object as a veil that the perverse subject erects in front of the Thing in order to avoid an encounter with it.

However, this problematic relation to the phallus is not exclusive to fetishism but extends to all the perversions. "The whole problem of the perversions consists in conceiving how the child, in his relation to the mother . . . identifies himself with the imaginary object of [her] desire [i.e. the phallus]."

This is why the preoedipal imaginary triangle plays such an important role in the perverse structure.

In the perversions, the phallus can only function as veiled.

Perversion is also a particular way in which the subject situates himself in relation to the drive.

In perversion, the subject locates himself as object of the drive, as the means of the Other's jouissance.

This is to invert the structure of fantasy, which is why the formula for perversion appears as a <> $ in the first schema in "Kant with Sade", the inversion of the matheme of fantasy.

The pervert assumes the position of the object-instrument of the "will-to-enjoy" (volonté-de-jouissance), which is not his own will but that of the big Other.

The pervert does not pursue his activity for his own pleasure, but for the enjoyment of the big Other.

He finds enjoyment precisely in this instrumentalization, in working for the enjoyment of the Other. "The subject here makes himself the instrument of the Other's jouissance."

Thus in scopophilia (also spelled scoptophilia), which comprises exhibitionism and voyeurism, the pervert locates himself as the object of the scopic drive.

In sadism/masochism, the subject locates himself as the object of the invocatory drive.

The pervert is the person in whom the structure of the drive is most clearly revealed, and also the person who carries the attempt to go beyond the pleasure principle to the limit, "he who goes as far as he can along the path of jouissance."

Freud's remark that "the neuroses are the negative of the perversions" has sometimes been interpreted as meaning that perversion is simply the direct expression of a natural instinct which is repressed in neurosis.

However, Lacan rejects this interpretation entirely.

Firstly, the drive is not to be conceived of as a natural instinct which could be discharged in a direct way; it has no zero degree of satisfaction.

Secondly, as is clear from the above remarks, the pervert's relation to the drive is just as complex and elaborated as that of the neurotic.

From the point of view of genetic development, perversion is at the same level as neurosis; both have reached the third "time" of the Oedipus complex.

Perversion therefore "presents the same dimensional richness as [a neurosis], the same abundance, the same rhythms, the same stages."

It is therefore necessary to interpret Freud's remark in another way: perversion is structured in an inverse way to neurosis, but is equally structured.

While neurosis is characterized by a question, perversion is characterised by the lack of a question; the pervert does not doubt that his acts serve the jouissance of the Other.