In other words it is the signifier as such, as instituted through symbolic castration, that introduces the idea of recapturing fullness, a fullness which is desired exactly because it is posited as lost/sacrificed. This fullness is in fact impossible to recapture because it was never part of ourselves.
Even the pre-symbolic real in which nothing is lacking should not be conceived as a stage of fullness. In Crucial Problems for Psychoanalysis it is clearly stated that the real should not be understood as a raw and opaque mass (seminar of 2 December 1964). As Lacan also points out in his seminar on Anxiety, the non-lacking character of the real does not mean that the real is always full. On the contrary, it is plausible to conceive the real as full of holes. What it means is that it does not lack anything (seminar of 20 March 1963). There is no lack or absence in the real (II:313).
Lack is introduced then at the intersection of the real with the symbolic. It is the symbolic that entails lack.
Lack emerges in and through the symbolisation of the real. Before the introduction of the symbolic there is no lack and thats why we know that the real is not lacking; if it was lacking, lack would be introduced without the symbolic or before the introduction of the symbolic.
The real is related to lack exactly because in the process of symbolisation, the signifier produces the signified, creating the imaginary illusion of attaining the lost real. Sooner or later, the illusory character of this fixation of meaning is revealed. If the real is the domain of the inexpressible, the domain of death and inexpressible enjoyment (jouissance) then its presence, the encounter with the real, can only have as a consequence the revelation of the lack of our imaginary/symbolic constructs, of their inability to represent death and jouissance, to be real. (Stavrakakis 1999, 44)