Somewhere or other, Deleuze remarks that Darwin effects a Copernican revolution for thought. Yet in many respects, it seems that this revolution has gone almost completely unremarked in philosophy. In short, this revolution has scarcely been registered by philosophy. Here it is important to be precise. The claim that Darwin effected a Copernican revolution in thought does not refer to his magnificent contributions to biology. Nor is the suggestion that philosophy should become “Darwinistic”, reducing philosophical questions to questions of biology.

Rather, Darwin’s revolution is far more general and abstract. Setting aside his theory of biological speciation, Darwin’s contribution to philosophy resides in his understanding of difference. It could be said that Darwin’s motto is that individual difference makes the difference. Where, prior to Darwin, there was a sharp gulf separating difference inhabiting the individual and species-difference, Darwin shows how individual difference is productive of species-difference. In the former scheme, the individual and the species were understood as two distinct entities, with the species functioning as an ideal norm defining individuals, an essence, distinct and existing in its own right, and individuals being measured in terms of how closely they approach this ideal form.

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Under this model, essential differences or species-differences were treated as eternal and enduring characteristics shared by a plurality of individuals, whereas the individual differences falling outside species-differences were treated as mere accidents secondary to the essence or species. Darwin’s remarkable contribution was to show that individual difference is the motor of speciation or the genesis of form. As a result, form is no longer treated as an ideal norm or eternal essence to which the individual is subordinated, but rather form becomes a result or product of these individual differences. Species become not ideal and eternal, unchanging essences, but rather become statistical regularities within a population, produced as a result of the accumulation of individual differences through natural selection and reproduction. Where essentialist thought faces the problem of how it is possible to explain the heterogeneity of individuals, the issue now becomes that of it is possible to explain homogeneity insofar as heterogeneity is the norm. As Whitehead famously observes, “the abstract does not explain, but must be explained.”

From this perspective, the significance of Darwin for philosophy becomes clear: What Darwin’s thought challenges is the primacy of all essence/accident/individual and form/content theorization. After Darwin, it is difficult not to chuckle when we hear philosophers continue to harp on distinctions between form and content, scheme and content, type and token, essence and existence, norm and fact, and all the rest. One marvels at how legions of scholars continue to take Kant’s account of the role played by the categories in cognition, or how we get endless discussions of the aporetic relationship between scheme and content or type and token. For example, how can thinkers take seriously Adorno’s negative dialectic between form and non-conceptual differences? Have they not heard? Species-difference is an effect of individual difference, and species themselves are individuals, not ontological categories like essences that differ in kind from individuals. Somehow philosophy today has remained all too theological, all too Medieval.