“What is human reason?” asked Uncle Theory. He was, as usual, challenging the children. One little boy said he thought it had something to do with waking up alone.
It was just another morning amid the bruised hearts and Uncle was having none of it. “What on earth does your tiny heart, beating like a bird trapped in a barn, have to do with reason?” he shouted.
Baby Deleuze climbed on his desk and spoke up. “Suppose we imagine the subordination of difference to identity.” he said. “In ordinary terms difference is just an empirical relation between two terms each of which have an a priori identity– (“x is different from y”). But this notion of primacy can be inverted: identity persists, but it is now a secondary principle created by a prior relation between differentials (dx rather than not-x). Difference is no longer an empirical relation but becomes a transcendental principle that constitutes the sufficient reason of empirical diversity.”
(Thanks are due to: Smith, Daniel and Protevi, John, "Gilles Deleuze", The Stanford Encyclopedia of Philosophy (Winter 2011 Edition), Edward N. Zalta (ed.), http://plato.stanford.edu/archives/win2011/entries/deleuze/