We have done enough digging around to appreciate that Deleuze has framed his account of individuation and agency through an evolving critical engagement with evolutionary thinking that is rooted in his early rehabilitation of Henri Bergson's 1907 Creative Evolution and which draws widely on the advances of recent biology. For all the connections with biological science Deleuze's work remains philosophical in terms of its metaphysics of vitalism and the virtual.

Mark Hansen says:

Only in Difference and Repetition does Deleuze fully articulate the transcendental principle of difference central to his important work of the late 60s. As I have suggested, this articulation involves a certain break with Bergson and also, it must be stressed, with the biological realism with which Bergson theorizes the elan vital. Intended as a means of reaching a properly philosophical realm of analysis and directed against Bergson's determination of the life force as a counterpoint to entropy (which Deleuze perceives to involve a potentially crippling reliance on a thermodynamic model), this break involves a key revision in Deleuze's previous understanding of vital difference. Rather than deriving vital difference from Bergson's two forms of difference, as he had in Bergsonism...Deleuze now finds it necessary to posit a fundamentally separate and primordial form of difference (intensity) from which both of Bergson's forms are derived.