Gilles Deleuze, answered from the texts and cited to the page.
The task of philosophy, inherited from Nietzsche, is the overturning of Platonism — but not in the obvious sense (privileging copy over original, sensible over essence).1 The deeper Platonic distinction is not between essence and appearance but between two kinds of image-idol: the icon (legitimate copy, internally resembling the Idea) and the simulacrum (false claimant whose semblance is purely external).
To overturn Platonism is to affirm the simulacrum on its own terms — to articulate a being-of-difference constituted by internal difference (difference-in-itself) rather than by resemblance to a transcendent Idea. Identity and resemblance survive only as effects produced by the differential machinery of the simulacrum.23 This is transcendental empiricism: Ideas are immanent to experience as differential, problematic structures — multiplicities of singularities-events.4 The canonical question "What is X?" gives way to the minor questions "Who? Where? When? How? In what case?"5
Such a project, however, would not be peculiar to Nietzsche. The dual denunciation of essences and appearances dates back to Hegel or, better yet, to Kant. It is doubtful that Nietzsche meant the same thing. Moreover, this formula of reversal has the disadvantage of being abstract; it leaves the motiva¬ tion of Platonism in the shadows.The Logic of Sense, pp. 253–254
The problem is rather in the status and the position of this resemblance. Let us consider the two formulas: "only that which resembles differs" and "only differ¬ ences can resemble each other." These are two distinct readings of the world: one invites us to think difference from the standpoint of a previous similitude or identity; whereas the other invites us to think similitude and even identity as the product of a…The Logic of Sense, pp. 261–262
The eternal return is the same of the different, the one of the multiple, the resemblant of the dissimilar. Although it is the source of the preceding illusion, it engenders and maintains it only in order to rejoice in it, and to admire itself in it as though in its own optical effect, without ever falling into the adjoining error.Difference and Repetition, p. 161
Ideas are by no means essences. In so far as they are the objects of Ideas, problems belong on the side of events, affections, or accidents rather than on that of theorematic essences. Ideas are developed in the auxiliaries and the adjunct fields by which their synthetic power is measured. Consequently, the domain of Ideas is that of the inessential.Difference and Repetition, p. 247
The philosopher as such is a symptomatologist, a typologist and a genealogist. We can recognise the Nietzschean trinity of the "philosopher of the future": the philosopher-physician (the physician interprets symptoms), the philosopher-artist (the artist moulds types), the philosopher-legislator (the legislator determines rank, genealogy) (cf. PTG, VP IV).Nietzsche and Philosophy, pp. 75–76
Stated most fully in Difference and Repetition (1968) and The Logic of Sense (1969), with antecedents in the Nietzsche book of 1962 and in the Platonism essay eventually published in The Logic of Sense as the appendix on the simulacrum. The position is constructive, not deconstructive: the overturning of Platonism is what I called a rejuvenated Platonism, retrieving the Platonic project on a basis that no longer subordinates difference to identity. Held with full force across the authorship; the geology of morals in A Thousand Plateaus extends the same structural argument to social formations.