From the introduction to Ellen Pollak’s Incest and the English Novel, 1684-1814 : According to Derrida, the prohibition against incest is “the unstable center of structuralist thought.” But in Derrida’s hands, it becomes “the condition of the possibility of meaning.” As Pollak explains it, Derrida’s “sexual fable of the production of meaning” treats incest as “the ever-elusive condition of pure presence, whose endless deferral (differance) through prohibition is the locus of that orioginary lack on which the entire order of supplementarity (for Derrida, the sine qua non of meaning production and thus of writing) depends.”

She elaborates:

For Derrida, incest is the “point of orientation” for the system of signification in general, the point where the Transcendent Signified that is the reference point of all signs is promised, as well as, simultaneously, the point where the signified “conceals itself as that which would destroy at one blow the entire system of signification.” This “nonexistent point” is “always elusive,” or, what comes to the same thing, “always already inscribed in what it ought to escape or ought to have escaped, according to our indestructible mortal desire.”

In founding the system of signification and meaning, incest prohibitions also found the possibility for a distinction of nature and culture: “In the deconstructive account of Western philosophy . . . incest, far from standing outside the order of culture and prohibition, actually props that order up from within; it is itself constituted by prohibition. Incest occupies the place outside of culture that makes the very thinking of culture possible; like its prohibition, it stand on border that simultaneously enables and threatens the distinction between nature and culture. As such, it represents at once thae absence of those systems of difference that constitute culture and a fiction conceived to make it possible to think those differences.”

To explain (perhaps): Incest stands for pure self-presence because incest is union not with another but with oneself, a union with my own flesh, rather than a union of distinct flesh into one flesh. Incest aims at masturbatory pleasure, pleasure in my own flesh rather than the flesh of another. To cross out that possibility, as every culture does, is to admit the endless deferral of that moment of pure self-presence. The incest taboo is an admission that the transcendent signified is inaccessible. But that deferral and admission is the foundation of the possibility of meaning, because original supplementarity is the foundation of the possibility of meaning. Prohibition of incest is the Do Not Enter sign that prevent trespassors from gaining access to the pure, unsupplemented origin that cannot ever be reached anyway. Thus, just as the recognition of originary supplementation is the condition for the possibility of meaning, of signification systems, so the prohibition of incest is the condition for the possibility of the signification systems of culture.

Or, from another angle: Incest prohibitions are not natural, but cultural. Animals don’t observe these taboos. Yet, this cultural institution, the prohibition of incest, is the cornerstone of the cultural system itself. Here again is an aporia analogous to the aporia of supplement at the origin: The foundation stone of the cultural system doesn’t stand outside the cultural system, but is always already there within.