However, if structuralism ultimately identifies the subject with structure (the Other), Lacan intervenes, at this point, in a very Kantian manner: he introduces the subject as a correlative to the lack in the Other; that is, as correlative to the point where structure fails fully to close in upon itself.
He does this in two different ways. The first consists in introducing a moment of irreducible jouissance as the ‘proof of the subject’s existence’.
The second – and this is what interests us here – consists in defining the subject via the shifter ‘I’ in relation to the ‘act of enunciation’.
Lacan ‘s claim that there is no Other of the Other means that the Other and the statement have no guarantee of their existence besides the contingency of their enunciation.
This dependence cannot in principle be eliminated from the function of the Other, and this is precisely what attests to its lack. The subject of enunciation does not and cannot have a firm place in the structure of the Other; it finds its place only in the act of enunciation.
This amounts to saying that the depsychologizing of the subject does not imply its reducibility to a (linguistic or other) structure. The Lacanian subject is what remains after the operation of ‘de-psychologizing’ has been completed: it is the elusive, ‘palpitating’ point of enunciation.