what differentiates hysteria from psychosis is their different relation to the “enjoyment of the Other” (not the subject's enjoyment of the Other, but the Other who enjoys [in] the subject): a hysteric finds it unbearable to be the object of the Other's enjoyment, she finds herself “used” or “exploited,” while a psychotic willfully immerses himself in it and wallows in it. (A pervert is a special case: he posits himself not as the object of the Other's enjoyment, but as the instrument of the Other's enjoyment—he serves the Other's enjoyment.)
In neurosis, we are dealing with hysterical blindness or loss of the voice, that is, the voice or gaze are incapacitated; in psychosis, on the contrary, there is a surplus of the gaze or voice, for a psychotic experiences himself as gazed upon (paranoiac) or he hears (hallucinates) non‐existing voices. In contrast to both these stances, a pervert uses the voice or gaze as an instrument, he “does things” with them. The root of these shifts in the meaning of big Other is that, in the subject’s relation to it, we are effectively dealing with a closed loop best rendered by Escher’s famous image of two hands drawing each other. The big Other is a virtual order which exists only through subjects “believing” in it; if, however, a subject were to suspend its belief in the big Other, the subject itself, its “reality,” would disappear. The paradox is that symbolic fiction is constitutive of reality: if we take away the fiction, we lose reality itself. This loop is what Hegel called “positing the presuppositions.” This big Other should not be reduced to an anonymous symbolic field—there are many interesting cases where an individual stands for the big Other. One should think not primarily of leader‐figures who directly embody their communities (king, president, master), but rather of the more mysterious protectors of appearances—such as otherwise corrupted parents who desperately try to keep their child ignorant of their depraved lives, or, if it is a leader, then one for whom Potemkin villages are built.
This distinction between the neutral/absorbing zero and the zero of measure is not to be confused with another distinction which also relates to the psychoanalytic practice: the distinction between nothing and the void. Nothing is localized, like when we say “there is nothing here,” while the void is a dimension without limits. In psychoanalytic clinics, this couple is clearly operative in the distinction between psychosis and hysteria: in psychosis, we encounter so‐called “depersonalization” or the feeling of the loss of reality, which refers to a void; while in hysteria, this void is localized as a nothing, a specific dissatisfaction. What this means is that nothing is always a nothing within some specific framework: there is nothing within a frame where we expected something. The first task in the analysis of a psychotic is thus arguably the most difficult, but also the most crucial: that of “hystericizing” the psychotic subject, that is, transforming the void of his “depersonalization” into a hysterical dissatisfaction. The opposite of this transformation is the case of psychotic forclusion, where the excluded element throws the subject back into the void. But why? Because the excluded element—the Name‐of‐the‐Father—is not just one among the signifiers, but a signifier‐frame, a signifier which sustains the texture of an entire symbolic framework.
Perhaps, one should extend this to the very definition of humanity: what ultimately distinguishes humans from animals is not some positive feature (speech, tool‐making, reflexive thinking, etc.), but the rise of a new point of impossibility designated by Freud and Lacan as das Ding, the impossible‐real ultimate reference point of desire. The often noted experimental difference between humans and apes acquires here all its significance: when an ape is presented with an object out of reach, it will abandon it after a few failed attempts to grasp it and move on to a more modest object (a less attractive sexual partner, say), while a human will persist in its effort, remaining transfixed on the impossible object. This is why the subject as such is hysterical: precisely a subject who posits jouissance as an absolute; it responds to the absolute of jouissance in the form of unsatisfied desire. Such a subject is capable of relating to a term that remains outside the limits of the game; indeed, this relationship to a term “out‐of‐play” is constitutive of the subject itself.
Hysteria is thus the elementary “human” way of installing a point of impossibility in the guise of absolute jouissance. Is not Lacan’s il n’y a pas de rapport sexuel also such a point of impossibility constitutive of being human?
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 (S11, 185). This is to invert the structure of FANTASY, which is why the formula for perversion appears as a◇s/ in the first schema in ‘Kant with Sade' (Ec, 774), 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 instrumentalisation, in working for the enjoyment of the Other; ‘the subject here makes himself the instrument of the Other's jouissance' (E, 320). 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 (S11, 182–5). 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' (E, 323). 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 (Freud, 1905d: SE VII, 165). However, Lacan rejects this interpretation entirely (S4, 113, 250). 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 (S4, 251). Perversion therefore ‘presents the same dimensional richness as [a neurosis], the same abundance, the same rhythms, the same stages' (S4, 113). 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 (S4, 251). While neurosis is characterised 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.（Dylan Evans An Introductory Dictionary of Lacanian Psychoanalysis）