1. In a fairly late text (Tentamen Anagogicum, 1696), Leibniz declares that there are two “kingdoms” in nature that “interpenetrate without confusing or interfering with each other”: power and wisdom. The former denotes the “interior” relations of forces and efficient causes (i.e., physics) while the latter denotes the architectonic domain of final causes (the totality of formal determinations), i.e., metaphysics. The doctrine of pre-established harmony has the consequence that the reality of possibility is simply thought itself (Mercer reminds us that the doctrine of pre-established harmony is an extension of the sympathetic participation of each individual with the divine essence). Only a small but important difference separate Leibniz and Berkeley here: for Leibniz, ideas are not real beings but collapsing the distinction between ideas and spirits simply radicalizes Leibniz’s immanentism: individuals do not “have” or “contain” ideas but simply are ideas. An intentional idea is at the same time a reflexive idea just as the productive understanding of God is self-understanding.
But because Leibniz refuses the absolute immanence to which his doctrine is compelled, he must explain the difference between the confused and highly mediated understanding of the individual from that of God. And it is here that he introduces the notion of a “point of view”: the monad simply is a point of view. But instead of the optics so important for Descartes and Berkeley, Leibniz gives us topology (analysis situs). Berkeley’s optics raises space to the status of a third thing between perceiver/d; Leibniz’s conception of geometry provides us with the formal analysis of form as an account of perception in the monads (qua phenomenal) that, at the same time, explains their irreducible multiplicity (qua ontological): “the theory of similarities or of forms lies beyond mathematics and must be sought in metaphysics” (“On Analysis Situs”).
Yet perhaps the place Leibniz reserved for transcendence is merely a sign whose mode of signification is exactly how he would describe its referent: i.e., whose center is everywhere and circumference nowhere. In a letter to Mason, Leibniz affirms the principle that “a living being cannot die unless the whole universe dies (or perishes) as well”. But the theodical doctrine should not be read merely as a moral principle: this world—as the “optimal” possible world—is thus necessary. Yet it is Leibniz and not Spinoza who is ridiculed for his commitment to the necessity of the world when both men are committed to the doctrine of universal determinism as the ultimate the condition of possibility for the intelligibility of the world. If there is transcendence in Leibniz, it must consist in the possibility of rigorously differentiating the monad he calls God from any other monad.
2. The idealist tradition after Kant recognized that his decisive maneuver in the critical turn was to provide an account of transcendence only on the basis and possibility of immanence, i.e., that the restrictions on the use of concepts are legislated by reason itself: the immanence of thought and the transcendence of world (which goes under the quasi-religious name of finitude). Every idealist—and, for that matter, materialist—after Kant has repeated and re-affirmed this observation: that transcendence (to be beyond being, for example) must be immanent to itself and that immanence, being “in-itself”, must transcend itself (else it is not “in-itself”). To escape this dialectical solution, Deleuze proposes to conceive of immanence not as being-in-itself but as difference. Yet at the same time he declares the univocity of being as a redress to the Kantian legacy: philosophy concerns not the thought of difference (Hegel, Heidegger), which in any case must lead to idealism. Philosophy itself is nothing other than the expression of difference; the “method” of philosophy is deterritorialization or virtualization. This is why the plane of immanence is “the image of thought, the image thought gives itself of what it means to think” (and why the domain of the concept is the virtual while, importantly, the “discursive power of the function” pertains to the actual). The plane of immanence—as the critical point between the virtual and the actual—names the volatile unity of thought and being. Philosophy—this movement toward the virtual—would not be possible if the virtual were merely thought as “potential” or, similarly, if becoming were thought as the movement from the virtual (to the actual). The attempt to identify being and the event destroys philosophy. The plane of immanence names the condition of possibility for philosophy by the non-reversability of the lines from the virtual to the actual and in the other direction—because we must pass through the event. This and nothing more is meant by “materialism”: the plane of immanence not as a substratum but as the duality of thought and nature, neither in-itself (being) nor for-itself (act, entelechy), but affection or life.