According to Kant, as I understand him, nature has an orderliness that appears (or compels belief in) to have been ordered by a divine power, but that the validity of such an appearance can neither be proved or disproved by the power of (pure) reason. Darwin's theory shows (as I understand it) that all life is the product of successive random forces. Does Kant's philosophy remain unaffected by this Darwinian insight?

You're quite right about Kant. The purposiveness--orderliness--of organisms in particular and, indeed, of nature in general, while manifest in experience, cannot themselves, according to Kant, be proven from experience. In the Critique of Judgment (henceforth referred to as 'KU' and cited from James Creed Meredith's translation, revised by Nicholas Walker [Oxford University Press, 2007]), Kant explains that the principle of the intrinsic purposiveness of organisms "must be derived from experience....But owing to the universality and necessity which that principle predicates of such purposiveness, it cannot rest on merely empirical grounds, but must have some underlying a priori principle" (§ 66). Since, however, according to Kant, and in accordance with Kant's understanding of Newtonianism, nature itself is merely a realm of efficient causes, there is no room in nature for purposiveness (KU § 66), which leads to an antinomy of teleological judgment (KU §§. 69-78, esp. §§. 69-71), very roughly--Kant's conception of an antinomy is somewhat more complicated, but an exposition of it would take us too far afield--a tension between the claims that there is no purposiveness in nature and that there is purposiveness in nature. Kant concludes that it is necessary for the human capacity for reflective judgment--which is the subject of the Critique of Judgment, a title more literally rendered as Critique of the Power of Judgment, as it is translated by Paul Guyer for the edition of that work in the Cambridge Edition of the Works of Immanuel Kant--to conceive of organisms, and, indeed, of nature itself as purposive: "by the constitution of our cognitive faculties...we are absolutely incapable of forming any concept of the possibility of [a purposively ordered] world unless we think a highest cause operating designedly" (KU § 75; my bold). This, however, is no proof of God's existence. "But all that is permissible for us human beings," Kant writes later in § 75, "is the narrow formula: We cannot conceive or render intelligible to ourselves the purposiveness that must be introduced as the basis even of our knowledge of the intrinsic possibility of many natural things, except by representing it, and, in general, the world, as the product of an intelligent cause--in short, of a God."

It's not clear to me that Kant's view is at all affected by the evidence for Darwin's account of evolution that the 'modern synthesis' of Darwin's ideas with genetics has provided. For the "Darwinian insight," it seems to me, is a claim about how traits confer a reproductive advantage on organisms, which--in virtue of the work of geneticists--has been substantiated by our understanding of the efficient causal--that is, genetic--basis of traits. It seems to me that Kant would take Darwin simply to have made a claim about the efficient causal order of natural organisms, and not, therefore, to have shown anything about their purposiveness that would require Kant to reconceive his view that purposiveness itself cannot be proven from mere experience alone.

Let's go a step further. Although it has been claimed that Darwinism refutes the 'argument from design', it's not clear that it does so. After all, why not take the fact that so much is accomplished by such simple means--that organisms develop and change in virtue of the reproductive advantages of traits that are passed along to future generations in virtue of their genes--to be a further proof that there must be a designer? Now Kant himself would reject such 'dogmatism', on the grounds that even the inference from a complicated mechanism to a designer is itself unwarranted: "But suppose teleology brought to the highest pitch of perfection, what would it all prove in the end? Does it prove, for example, intelligent Being really exists?....We are unable...objectively to substantiate the proposition: There is an intelligent original Being" (KU § 75). But Kant's reasons for rejecting the argument from design rest on his theory of cognition, a theory presented in the Critique of Pure Reason, and if one rejects that theory of cognition in favor of a more empiricist theory--a rejection that of course would take quite some argumentation, which I can't even begin to go into here--then one might be able to retain some version of the argument from design after all, even while acknowledging the power of Darwin's insights.

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