A delicate problem animates chapter 3 of Difference and Repetition.  Deleuze wants to defend a pure concept of difference, an account of difference in itself, yet our experience is representational through and through.  Everywhere we are creatures of habit that recognize beings and therefore do not encounter difference.  We subordinate the beings of our experience to the same, similar, and the identical, assimilate what we experience to what we have experienced.  Wesen ist gewesen.  What, then, authorizes Deleuze to claim that there is something like difference in itself?  Is it not the case, as Hegel and Kant perhaps suggested, that everything is always already mediated or subordinated to the logic of representation (identity in the concept, analogy in the judgment, opposition among predicates, and resemblance in perception)?

In chapter 3 of Difference and Repetition Deleuze will present what might be called a sort of “anti-phenomenology” that authorizes an appeal to difference in itself.  He will claim that there is an experience in which we do, in fact, encounter difference in itself.  Where so much of phenomenology– and I know I’m not here being fair –sets out to demonstrate how we recognize things or how we always encounter them within a horizon of meaning (again a system of recognition), Deleuze will look at the dark side of experience, pointing to those moments where the system of meaning and recognition fails.  Thought, Deleuze will argue, only occurs under the force of an encounter.

…there is only involuntary thought, aroused but constrained within thought, and all the more absolutely necessary for being born, illegitimately, of fortuitousness in the world.  Thought is primarily trespass and violence, the enemy, and nothing presupposes philosophy:  everything begins with misoophy.  Do not count upon thought to ensure the relative necessity of what it thinks.  Rather, count upon the contingency of an encounter with that which forces thought to raise up and educate the absolute necessity of an act of thought or a passion to think…

Something in the world forces us to think.  This something is an object not of recognition but of a fundamental encounter.  What is encountered may be Socrates, a temple or a demon.  It may be grasped in a range of affective tones:  wonder, love, hatred, suffering.  In which tone, its primary characteristic is that it can only be sensed.  (DR, 139)

Everything goes wrong from the outset if we assimilate thought to simple cognition.  This is Deleuze’s primary reproach against so much of the history of philosophy, and would no doubt be his criticism of cognitive science which takes itself to study thought:  they assimilate thought to simple recognition.  Yet for Deleuze, thought is essentially rare.  We cognize and recognize all the time as creatures of habit (the first synthesis of repetition in Chapter 2), but we do not yet think.  It is only as a shock to our system that we begin to think.  There can thus be no method of thought, nor a willing of thought, because in its initial phase, it is entirely passive.  We can only undergo the force of a fortuitous encounter that involuntarily instigates thought within us (and clearly this is often a very unpleasant thing).  In Lacanian terms, we could say that thought is the result of trauma, of the missed encounter, of that that evades the symbolic net we throw over the world to render it re-cognizable.

read on!

For Deleuze, thought is an encounter with the different that produces difference.  If it can only be sensed, this is because it cannot be perceived.  Here we should think of Hussar’s accounts of perception or even Heidegger’s account of alethetheia.  Perception implies recognition.  “That is a glass.”  “That is a book.”  “There goes my wife.”  Recognition is re-cognition.  It is that which can be remembered or subsumed under an extant concept.  But thought is the un-re-cognizable, and therefore an encounter with something that can’t be subsumed under any pre-existing concept, meaning, or memory.  If it can only be sensed– what Deleuze calls the “sentiendum”; and his book is designed to be a sort of sentiendum –then that is because we’ve encountered something that can’t be perceived or recognized; something that departs from all “conceptual schemes”.  “Something is different here, yet I have no idea what it might be precisely because there isn’t yet any concept or meaning for it.  This is why Deleuze claims that thought instigates a discordant functioning of the faculties.  Where, in perception, memory functions to show how the current experience resembles other past experiences, in the encounter thought is in discord with memory.  No wonder Deleuze was fascinated with Klossowski’s Roberte novels!  In the encounter we discover the immemorial precisely because there is no recollection, no “system of anticipations” as in Husserl, that could converge in a synthesis on this thing that can only be sensed.  And this is why the encounter generates the cogitandum, or that which can only be thought:  the unprecedented.  Thought is not the syllogism, nor subsumption under an established concept, but the invention of that for which there is yet no concept.

If thought is rare, then this is because thought for Deleuze is essentially invention and discovery.  He restricts thought to these adventures of discovery and invention in the arts, mathematics, and the sciences.  Here Kuhn is helpful.  Kuhn draws the distinction between normal science and revolutionary science.  Normal science solves problems within an existing model or paradigm.  Revolutionary science is what takes place when the paradigm itself is transformed.  Deleuze would reserve the name of thought for the latter.  We can see how this might work in a variety of scientific and mathematical contexts.  The irregular orbit of the planet Mercury is a sentiendum in the sciences.  It is something that doesn’t fit with the established Newtonian models.  The Newtonians attempt to assimilate this orbit to the Newtonian models.  “There must be a hidden variable, a moon that we haven’t explored or perhaps even a planet we haven’t yet observed!”  There is something that preserves the model (Newtonianism) that we haven’t yet observed.  Thought is what takes place with Einstein.  It is not that we haven’t yet observed the missing mass, but rather that we’ve gotten the theory of gravity wrong.  We must entirely rethink gravity in light of this exception (cogitandum).  Or again we might think of the Pythagoreans that discovered irrational numbers.  Here we have a cautionary tail of when thought does not take place and where re-cognition takes precedence.  They repress the discover of irrational numbers when trying to find the diagonal of certain squares and even club one of their followers to death when he tries to discuss irrational numbers publicly.  Everything, they contend, must consist of harmonious ratios.  Here is the active suppression of thought or an attempt to domesticate the encounter or that which forces thought.  Where the discovery of irrational numbers should have opened an entirely new field of mathematics, it’s instead brutally repressed.  And should this be how we think of the trans person?  Not as the person to be assimilated to one sexual position or the other, but as the person that calls us to rethink our entire concept of gender and sexuality?  And this, for Deleuze, is what it ultimately comes down to:  all genuine thought is poietic or inventive and it is only those moments that send us on these adventures that deserve to be called thought.