For Deleuze, perhaps to exist was not just to make a difference: it was to be a difference, to be uniquely configured by the effects of the singular flows within the configuration spaces by which a thing becomes what it individually is. One wonders what exactly Deleuze would now point to as the Source of difference in what exists? The vagueness of species is predicated on the difference of the individual.
Beneath the general operation of laws, however, there always remains the play of singularities. Cyclical generalities in nature are the masks of a singularity which appears through their interferences; and beneath the generalities of habit in moral life we rediscover singular processes of learning. The domain of laws must be understood, but always on the basis of a Nature and a Spirit superior to their own laws, which weave their repetitions in the depths of the earth and of the heart, where laws do not yet exist. The interior of repetition is always affected by an order of difference: it is only to the extent that something is linked to a repetition of an order other than its own that the repetition appears external and bare, and the thing itself subject to the categories of generality.
--Difference and Repetition (tr. Paul Patton, 1994), p. 25.