Zupančič, Alenka. Ethics of the Real: Kant and Lacan. New York: Verso, 2000.
The advent of the subject of practical reason coincides with a moment that might be called a moment of ‘forced choice’.
Paradoxical as this may seem, the forced choice at issue here is none other than the choice of freedom, the freedom that first appears to the subject in the guise of psychological freedom.
It is essential to the constitution of the subject that she cannot but believe herself free and autonomous.
The subject is presumed to be free , yet she cannot disclose this freedom in any positive way, cannot point to it by saying:’This act of mine was free; this precise moment I was acting freely.’
Instead, the more she tries to specify the precise moment at which freedom is real, the more it eludes her, ceding its place to (causal) determination, to the pathological motives which were perhaps hidden from view at first glance.

The left side of the schema presents the ‘fact of the subject’, the fact that the subject is, so to speak, free by definition, that the subject cannot but conceive of herself as free.
The right side illustrates the choice the ethical subject faces, in which she must choose herself either as pathological or as divided.
The paradox, however, is that the subject cannot choose herself as pathological (S) without ceasing to be a subject as a result. The choice of the S is an excluded, impossible choice.
🙂 Pathological means here to be fully determined by internal causes, hate/love/jealousy/fear/anger etc, and to be determined strictly by pathological motives would preclude freedom.
The other choice would simply be that of choosing oneself as subject, as the ‘pure form’ of the subject, which is the form of the division as such.
We might also say that in this case the subject chooses herself as subject and not as (psychological) ‘ego’, the latter being understood — in all its profundity and authenticity — as the locus of the pathological. 32