Main article: Différance
Crucial to Derrida's work is the concept of différance,
a complex term which refers to the process of the production of
difference and deferral. According to Derrida, all difference and all
presence arise from the operation of différance.To deconstruct philosophy is therefore[further explanation needed] to think carefully within philosophy about philosophical concepts in terms of their structure and genesis. Deconstruction questions the appeal to presence by arguing that there is always an irreducible aspect of non-presence in operation. Derrida terms this aspect of non-presence différance. Différance is therefore the key theoretical basis of deconstruction. Deconstruction questions the basic operation of all philosophy through the appeal to presence and différance. Derrida argues that différance pervades all philosophy because "What defers presence [...] is the very basis on which presence is announced or desired in what represents it, its sign, its trace". Différance therefore pervades all philosophy because all philosophy is constructed as a system through language. Différance is essential to language because it produces "what metaphysics calls the sign (signified/signifier)".
In one sense, a sign must point to something beyond itself that is its meaning so the sign is never fully present in itself but a deferral to something else, to something different. In another sense the structural relationship between the signified and signifier, as two related but separate aspects of the sign, is produced through differentiation. Derrida states that différance "is the economical concept", meaning that it is the concept of all systems and structures, because "there is no economy without différance [...] the movement of différance, as that which produces different things, that which differentiates, is the common root of all the oppositional concepts that mark our language [...] différance is also the production [...] of these differences."Différance is therefore the condition of possibility for all complex systems and hence all philosophy.
Operating through différance, deconstruction is the description of how non-presence problematises the operation of the appeal to presence within a particular philosophical system. Différance is an a-priori condition of possibility that is always already in effect but a deconstruction must be a careful description of how this différance is actually in effect in a given text. Deconstruction therefore describes problems in the text rather than creating them (which would be trivial). Derrida considers the illustration of aporia in this way to be productive because it shows the failure of earlier philosophical systems and the necessity of continuing to philosophise through them with deconstruction.
