Clark continues his examination of Derrida's différance and Heidegger's ontological difference with an extended excerpt from Ousia and Gramme. Here's a couple answers from an interview of the same period, where Derrida lays out the four facets of différance, the fourth being the one from his essay, anticipating a difference to come.

Ronse: ...Much has been said above about the a of différance. What does it signify?

Derrida: I do not know if it signifies at all--perhaps something like the production of what metaphysics calls the sign (signified/signifier). You have noticed that this a is written or read, but cannot be heard. And first off I insist upon the fact that any discourse--for example ours, at this moment--on this alteration, this graphic and grammatical aggression, implies an irreducible reference to the mute intervention of a written sign. The present participle of the verb différer, on which this noun is modeled, ties together a configuration of concepts I hold to be systematic and irreducible, each one of which intervenes, or rather is accentuated, at a decisive moment of the work. First, différance refers to the (active and passive) movement that consists in deferring by means of delay, delegation, reprieve, referral, detour, postponement, reserving. In this sense, différance is not preceded by the originary and indivisible unity of a present possibility that I could reserve, like an expenditure that I would put off calculatedly or for reasons of economy. What defers presence on the contrary, is the very basis on which presence is announced or desired in what represents it, its sign, its trace...

Ronse: From this point of view différance is an economical question?

Derrida: I would even say that it is the economical concept, and since there is no economy without différance, it is the most general structure of economy, given that one understands by economy something other than the classical economy of metaphysics, or the classical metaphysics of economy. Second, the movement of différance, as that which produces different things, that which differenciates, is the common root of all the the oppositional concepts that mark our language, such as, to take only a few example, sensible/intelligible, intuition/signification, nature/culture, etc. As a common root, différance is also the element of the same (to be distinguished form the identical) in which these oppositions are announced. Third, différance is also the production, if it can still be put this way, of these differences, of the diacriticity that the linguistics generated by Saussure, and all the structural sciences modeled upon it, have recalled is the condition for any signification and any structure. These differences--and, for example, the taxonomical science which they may occasion--are the effects of différance; they are neither inscribed in the heavens, nor in the brain, which does not mean that they are produced by the activity of some speaking subject. From this point of view, the concept of différance is neither simply structuralist, not simply geneticist, such an alternative itself being an "effect" of différance. I would even say, but perhaps we will come to this later, that it is not simply a concept...

Ronse: I also have been struck that already in your essay on "Force and Signification" différance (but you did not yet call it that) led you back to Nietzsche (who linked the concept of force to the irreducibility of differences), and later to Freud, all of whose opposed concepts you showed to be governed by the economy of différance, and finally, always, above all, to Heidegger.

Derrida: Yes, above all. What I have attempted to do would not have been possible without the opening of Heidegger's questions. And first, since we must proceed rapidly here, would not have been possible without the attention to what Heidegger calls the difference between Being and beings, the ontico-ontological difference such as, in a way, it remains unthought by philosophy. But despite this debt to Heidegger's thought, or rather because of it, I attempt to locate in Heidegger's text--which, no more than any other, is not homogeneous, continuous, everywhere equal to the greatest force and to all the consequences of its questions--the signs of a belonging to metaphysics, or to what he calls ontotheology. Moreover, Heidegger recognizes that economically and strategically he had to borrow the syntaxic and lexical resources of the language of metaphysics, as one always must do at the very moment that one deconstructs this language. Therefore we must work to locate these metaphysical holds, and to reorganize unceasingly the form and sites of our questioning. Now, among these holds, the ultimate determination of difference as the ontico-ontological difference--however necessary and decisive this phase may be--still seems to me, in a strange way, to be in the grasp of metaphysics. Perhaps then, moving along lines that would be more Nietzschean than Heideggerean, by going to the end of this thought of the truth of Being, we would have to become open to a différance that is no longer determined, in the language of the West, as the difference between Being and beings. Such a departure is doubtless not possible today, but one could show how it is in preparation. In Heidegger, first of all. Différance--fourth--therefore would name provisionally this unfolding of difference, in particular, but not only, or first of all, of the ontico-ontological difference.

P. 8-10

I think Derrida's doing a hedgehog here. "Not possible today", but when someone actually gets around to demonstrating this more primordial difference, Derrida will have been there already.  ¶ 8:30 PM