“After a long period in which each pursued his own interests, Deleuze and Guattari published a last collaboration in 1991, What Is Philosophy? In answering their title question, Deleuze and Guattari seek to place philosophy in relation to science and art, all three being modes of thought, with no subordination among them. Thought, in all its modes, struggles with chaos against opinion. Philosophy is the creation or construction of concepts; a concept is an intensive multiplicity, inscribed on a plane of immanence, and peopled by “conceptual personae” which operate the conceptual machinery. A conceptual persona is not a subject, for thinking is not subjective, but takes place in the relationship of territory and earth. Science creates functions on a plane of reference. Art creates “a bloc of sensation, that is to say, a compound of percepts and affects” (WP, 164).
We will deal with Deleuze and the arts in some detail below. In discussing What is Philosophy?, let us concentrate on the treatment of the relation of philosophy and science. We should remember at the outset that the nomad or minor science evoked in A Thousand Plateaus is not the Royal or major science that makes up the entirety of what Deleuze and Guattari call ‘science’ in What is Philosophy?. The motives for this conflation are unclear; in the eyes of some, this change considerably weakens the value of the latter work. Be that as it may, in What is Philosophy? Deleuze and Guattari vigorously deny that philosophy is needed to help science think about its own presuppositions (“no one needs philosophy to reflect on anything” [WP 6]). Instead, they emphasize the complementary nature of the two. First, they point out a number of similarities between philosophy and science: both are approaches to “chaos” that attempt to bring order to it, both are creative modes of thought, and both are complementary to each other, as well as to a third mode of creative thought, art. Beyond these similarities, Deleuze and Guattari distinguish between philosophy as the creation of concepts on a plane of immanence and science as the creation of functions on a plane of reference. Both relate to the virtual, the differential field of potential transformations of material systems, but in different ways. Philosophy gives consistency to the virtual, mapping the forces composing a system as pure potentials, what the system is capable of. Meanwhile, science gives it reference, determining the conditions by which systems behave the way they actually do. Philosophy is the “counter-effectuation of the event,” abstracting an event or change of pattern from bodies and states of affairs and thereby laying out the transformative potentials inherent in things, the roads not taken that coexist as compossibles or as inclusive disjunctions (differentiation, in the terms of Difference and Repetition), while science tracks the actualization of the virtual, explaining why this one road was chosen in a divergent series or exclusive disjunction (differenciation, according to Difference and Repetition). Functions predict the behavior of constituted systems, laying out their patterns and predicting change based on causal chains, while concepts “speak the event” (WP 21), mapping out the multiplicity structuring the possible patterns of behavior of a system—and the points at which the system can change its habits and develop new ones. For Deleuze and Guattari in What is Philosophy?, then, science deals with properties of constituted things, while philosophy deals with the constitution of events. Roughly speaking, philosophy explores the plane of immanence composed of constellations of constitutive forces that can be abstracted from bodies and states of affairs. It thus maps the range of connections a thing is capable of, its “becomings” or “affects.” Science, on the other hand, explores the concretization of these forces into bodies and states of affairs, tracking the behavior of things in relation to already constituted things in a certain delimited region of space and time (the “plane of reference”). How do concepts relate to functions? Just as there is a “concept of concept” there are also “concepts of functions,” but these are purely philosophical creations “without the least scientific value” (WP 117). Thus concrete concepts like that of “deterritorialization” are philosophical concepts, not scientific functions, even though they might resonate with, or echo, scientific functions. Nor are they metaphors, as Deleuze and Guattari repeatedly insist:
Of course, we realize the dangers of citing scientific propositions outside their own sphere. It is the danger of arbitrary metaphor or of forced application. But perhaps these dangers are averted if we restrict ourselves to taking from scientific operators a particular conceptualizable character which itself refers to non?scientific areas, and converges with science without applying it or making it a metaphor (Deleuze 1989: 129).
Deleuze and Guattari’s refusal to recognize that their work contains metaphors is due to their struggle against the “imperialism” of the signifying regime, a major theme in both Anti-Oedipus and A Thousand Plateaus: not every relation between different intellectual fields can be grasped by the most common notions of “metaphor,” reliant as they are on the notion of a transfer of sense from primary to secondary signification.” (tratto dalla Stanford Encyclopedia of Philosophy)