On Sunday, 4/21/13, we recorded our discussion on chapters 1-3 of What Is Philosophy? (1991). Go listen to the episode. Gilles Deleuze was a recent French philosopher (he died in 1995) who has probably been requested as much or more than any other figure by our listeners. His style is highly idiosyncratic: difficult somewhat in the manner of the other recent French figures we've covered, but frankly, quite a lot more fun; his work with Lacanian psychotherapist and political activist Felix Guattari in particular is very creative and riddled with jokes.
The main task of What Is Philosophy?, the pair's final work together (Guattari died not long after) seems to be setting up a new conceptual framework for understanding what philosophy is and how it differs from science and art. What is philosophy? It's the creation of concepts, specifically complex and interesting ones, that enable us to see the world in a different way. No concept is simple: each contains as components other concepts, meaning that they tend to be created in batches. It's a very anti-foundationalist view: concepts are active creations performed on a "plane of immanence," which you can think of as a pre-philosophical field of intuitions and sensibilities.
I would describe such a plane as a vague "representation of the world," but Deleuze's epistemology is radical along the lines of late William James and many post-Kantians, meaning that he doesn't make a real distinction between the representation and the world; they're just different aspects of the world (he highly praises Spinoza's idea of mental and physical aspects of all of creation). So the plane is a plane of immanence precisely because, from the point of view of that plane, there is no outside. The plane is not immanent to anything: it's not the field of experience behind which transcendent things-in-themselves or God work, and Deleuze even objects to Husserl's move of finding transcendent objects within experience (i.e. by perceiving one part of an object I posit that there are indefinitely many more unseen aspects, such that the object as a whole transcends my experience).
At the same time, different philosophies employ different planes of immanence, such that it's sometimes hard when you're reading different philosophers or even different periods of the same philosopher to figure out whether they're talking on the same plane. The plane determines what's going to be considered a legitimate and pressing philosophical problem, which the concepts are then created to articulate and address. This means that for any philosophy, much of the work is actually done pre-philosophically, undercover. The plane is actually part of the philosophy, and emerges more-or-less at the same time as the philosophical concepts themselves, as a necessarily unarticulated "image of thought," i.e. an idea of what thinking is supposed to really be, what is "due to thought by right." Is thought remembering, as Plato conceived it, or interpretation of received tradition, or the feigned ignorance and doubt of Descartes, etc. etc.?
The third element of a philosophy is its "conceptual personae," which are like the characters we see within and "behind" the philosophy. I use the quotes because it's not a matter of knowing the philosopher's biography, but of the character the philosopher makes of himself, e.g. the "Idiot" in Descartes who doubts everything. Not all of these personae represent the author, e.g. Plato has Socrates stand in for himself but also created other characters like Callicles that serve as icons for other positions. The personae are what give life and coherence to the philosophical concepts. The concepts to us as "signed" by the author, so that talking about the Cogito without thinking of it as Descartes's Cogito will only lead to confusion. So creating a philosophy (explicitly creating the concepts) also involves positing the corresponding plane of immanence and imagining and communicating the relevant conceptual personae.
This structure leads Deleuze to characterize apparent disputes in philosophy as typically people not on the same plane talking past each other. Truth itself is an element defined on a plane; there are no standards external to a plane by which to judge a philosophy. Instead of judging whether a philosophy is true, Deleuze thinks the big question is whether it is interesting and important, which is tantamount to figuring out, in part, whether the plane in question is where you're at given your culture, intellectual climate, and other factors. At the same time, his prohibition of transcendence as somehow contrary to the structure of doing philosophy itself amounts to a strong advocation of a fairly narrow set of philosophical positions, so he's not all hippy dippy "whatever you think is fine" in the way this might sound. Likewise, he stresses that these planes are not descriptions of an individual's subjective world-view; like Fregean senses, these planes are intersubjective, which is the same, for these phenomenology-influenced folks, as objective; there's simply no sense to be made of the term "objective" apart from the fact that different people at different times can go back and verify some alleged event or fact.
Deleuze stresses that these concepts are different than propositions, and you can't just try to translate the elements of a philosophical concept into propositions without turning them into a bunch of half-baked, insufficiently scientific opinions. Science is not in the business of creating concepts, but of using already created, utilitarian concepts (e.g. a word like "momentum" is shorthand for a bunch of observed phenomena; the scientist needn't ask what momentum REALLY is in the way that a philosopher would) to track regularities in states of affairs. Art likewise does not create concepts, but creates "percepts" and "affects" (note that these terms, unlike "perceptions" and "emotions" refer to public entities, not to private mental states of individuals).
For the discussion, we brought on longtime Deleuze fan and Ph.D. in rhetoric Daniel Coffeen. To get a sense of what he's about, go listen to the course he taught in rhetoric at UC Berkeley in 2008. As a self-proclaimed sophist, he provided an interesting foil to our usual method of trying to carefully suss out the meaning of the text and fit its lessons into our analytic frameworks. Instead, he emphasized the life-changing power of being knocked out by a new and powerful philosophical point of view, which is not at all different from discovering a new and visionary artist.