Deleuze considers traditional notions of space and time as unifying forms imposed by the subject. Therefore he concludes that pure difference is non-spatio-temporal; it is an idea, what Deleuze calls “the virtual”. (The coinage refers not to the “virtual reality” of the computer age, but to Proust’s definition of what is constant in both the past and the present: “real without being actual, ideal without being abstract”.

Wikipedia: As of January 4, 2010