Like differance, the expression is deliberately ambiguous, suppleer can mean either 'to supplement' or 'to supplant'. Derrida adopts the term 'supplement' from [[Jean-Jacques Rousseau, who argues in his essay on the origins of language that writing is no more than a supplement to, or parasite on, a natural spoken language, and who notes in his Confessions that masturbation is a 'dangerous supplement' to normal sexual intercourse. Derrida contends that, if speech has to be supplemented or supplanted by writing, it cannot be naturally self-sufficient and must therefore be characterized by an absence or gap, which he describes as an 'originary lack' Language does not, that is, originate in a natural state of completion as there is no extra-linguistic point of origin, but merely the 'originary lack'. It is the logic of supplementarity that makes nature or speech appear to be the prior term; at the same time, the chain of supplements or substitutions reveals the lack within it. Any attempt to find a pure point of origin, such as Husserl's attempt to ground phenomenology in pure perception, can be shown to follow the same logic and to mistake a supplement for an origin. Masturbation is a supplement, but if it is to function as such, it must resemble what it repalces; it may be a form of autoeroticism, but it still focuses on the imagined object that can never be possessed.
obscene supplement of the law
Here, however, it would be productive to introduce the distinction between the public symbolic Law and its obscene supplement: the notion of the obscene superego double-supplement of Power implies that there is no Power without violence. Power always has to rely on an obscene stain of violence, political space is never "pure" but always involves some kind of reliance on "pre-political" violence. Of course, the relationship between political power and pre-political violence is one of mutual implication: not only is violence the necessary supplement of power, (political) power itself is always-already at the roots of every apparently "non-political" relationship of violence. The accepted violence and direct relationship of subordination in the Army, Church, family and other "non-political" social forms is in itself the "reification" of a certain ethico-political struggle and decision - what a critical analysis should do is to discern the hidden political process that sustains all these "non-" or "pre-political" relationships. In human society, the political is the encompassing structuring principle, so that every neutralization of some partial content as "non-political" is a political gesture par excellence.
Žižek's argument is that it is this spectral supplement that constitutes the basis of all ideologies. Furthermore, he avers that reality itself depends on this supplement. This concept relies on our understanding the distinction between reality and the Real. We have no access to the Real because our world is always mediated by the Symbolic. Reality, as we know it, therefore, is always Symbolic. However, the Symbolization of the Real is, and cannot be, complete. The Symbolic can never saturate the Real and so, consequently, there is always some part of the Real which remains unsymbolized. What cannot be accommodated in the Symbolic produces a fundamental antagonism. It is this part of the Real that returns to haunt reality in the guise of the spectral supplement.
The spectre conceals the piece of the Real which has to be forsaken if reality (in the guise of the Symbolic) is to exist. And it is here, in the spectral supplement, that Žižek locates the foundation or kernel of all ideologies. All of which is another way of saying that reality and ideology are mutually implicated in each other. One cannot exist without the other.