What we are thus arguing is not simply that ideology also permeates the alleged extraideological strata of everyday life, but that this materializati… - Slavoj Žižek

The famous MacGuffin , the Hitchockian object, the pure pretext whose sole role is to set the story in motion but which is in itself nothing at all - the only significance of the MacGuffin lies in the fact that it has some significance for the characters - that it must seem to be of vital importance to them... - that's a MacGuffin, a pure nothing which is non the less efficient... what Lacan calls object petit a: a pure void which functions as the object cause of desire.

This is probably the fundamental dimension of 'ideology': ideology is not simply a 'false consciousness', an illusory representation of reality, it is rather this reality itself which is already to be conceived as 'ideological' - 'ideological' is a social reality whose very existence implies the non-knowledge of its participants as to its essence -that is, the social effectivity, the very reproduction of which implies that the individuals 'do not know what they are doing'. 'Ideological is not the false consciousness of a (social) being but this being itself in so far as it is supported by "false consciousness"'. Thus we have finally reached the dimension of the symptom, because one of its possible definitions would also be 'a formation whose very consistency implies a certain non-knowledge on the part of the subject': the subject can 'enjoy his symptom' only in so far as its logic escapes him - the measure of the success of its interpretation is precisely its dissolution.

The symptom is not only a cyphered message, it is at the same time a way for the subject to organize his enjoyment - that is why, even after the completed interpretation, the subject is not prepared to renounce his symptom.