Freud uses the term Verleugnung to denote "a specific mode of defence which consists in the subject's refusing to recognize the reality of a traumatic perception."
He introduces the term in 1923 in connection with the castration complex, the traumatic perception being the sight of the female genitalia; when children first discover the absence of the penis in the girl, they "disavow the fact and believe that they do see a penis all the time."
Psychosis and Fetishism
Freud continues to employ the term throughout the rest of his work, linking it specifically both to psychosis and to fetishism.
"Splitting of the Ego"
In these clinical conditions, disavowal is always accompanied by the opposite attitude (acceptance of reality), since it is "rarely or perhaps never" possible for "the ego's detachment from reality to be carried through completely."
The coexistence in the ego of these two contradictory attitudes to reality leads to what Freud terms "the splitting of the ego."
Repression and Foreclosure
While Freud's use of the term is quite consistent, he does not distinguish the term rigorously from the other related operations.
Lacan, however, works the term into a rigorous theory, relating it and contrasting it specifically with the operations of repression and foreclosure.
Whereas Freud had only linked disavowal to one form of perversion, Lacan makes it the fundamental operation in all forms of perversion.
And whereas Freud had also linked disavowal with psychosis, Lacan limits disavowal exclusively to the structure of perversion.
Disavowal is the fundamental operation in perversion, just as repression and foreclosure are the fundamental operations in neurosis and psychosis.
Thus, in Lacan's account, disavowal is one way of responding to the castration of the Other, whereas the neurotic represses the realization of castration, the pervert disavows it.
Like Freud, Lacan asserts that disavowal is always accompanied by a simultaneous acknowledgement of what is disavowed.
Thus the pervert is not simply ignorant of castration; he simultaneously knows it and denies it.
Whereas the term disavowal originally denotes, in Freud's work, only one side of this operation (the side of denial), for Lacan the term comes to denote both sides, the simultaneous denial and recognition of castration.
Lack and Desire
Whereas Freud relates disavowal to the perception of the absence of the penis in women, Lacan relates it to the realization of the absence of the phallus in the Other.
The traumatic perception is, in Lacan's account, the realization that the cause of desire is always a lack.
It is this realization that disavowal concerns; disavowal is the failure to accept that lack causes desire, the belief that desire is caused by a presence (e.g. the fetish).