In opposite to the thought of similarity, Deleuze raises a thought of difference. A thought that, instead of recognizing and associate the similar things, recognize what is different and thinks it singularly. "The freeing of difference requires thought without contradiction, without dialectics, without negation; thought that accepts divergence; affirmative thought whose instrument is disjunction; thought of the multiple-of the nomadic and dispersed multiplicity that is not limited or confined by the constraints of the same" [1] According to Foucault, in his essay devoted to Deleuze’s thought, there are two main factor impeding to think the difference: 1. Subjection to common sense, which recognizes the similar, divides and characterizes. 2. Subjection to categories that "suppress anarchic difference, divide differences into zones, delimit their rights, and prescribe their task of specification with respect to individual beings" [2] It is necessary to design an "acategorical thought".
[1] [2] FOUCAULT, Michel. Theatrum Philosophicum