There is increasing evidence that there is an evolved "moral grammar" in human brains (which in some respects resembles Kantian moral philosophy). My question is, is it possible to have an ethical system that is entirely rational and unreliant on "hardwired" beliefs? Obviously any moral theory that relies on evolution commits the naturalistic fallacy (what helps animals to survive and reproduce has no bearing on what is good and bad). Case in point is utilitarianism, trumpeted as an entirely secular and rational moral philosophy. But why would "anti-utilitarianism"--the ethical theory that prescribes the greatest pain for the greatest number--be, logically speaking, any less valid than utilitarianism? The assumption that pain is bad and pleasure is good appears to be "hardwired" and without rational basis. These questions leave me in some doubt about the viability of moral philosophy, since all moral theories seem to include premises that I have no reason to accept.

You pose one of the great challenges confronting philosophical ethics: explaining the rational basis of morality. If your last claim--that all moral theories include premises you have no reason to accept--is correct, then I don't see how the challenge can be met. A number of philosophers have rejected this claim, however. Kant, for example, suggested that morality is grounded by premises you are rationally bound to accept. According to Kant, simply being a free agent requires you to accept the rational force of certain imperatives, and these imperatives then provide the basis or foundation of your moral obligations.

Note that If Kant is correct, what grounds morality is not any biological fact about the ways in which our brains are hardwired. Rather, it is the metaphysical nature of rational agency that lies at the foundation of ethics. Consequently, any rational agent--human or otherwise--will be bound by the same obligations that bind you and me.

Of course, it is not at all clear whether Kant's strategy can succeed; and over the years, it has had many critics. Some have objected to Kant's claim that there are imperatives we are rationally bound to accept merely in virtue of being free agents. Others have wondered how we could possibly derive the obligations of morality from foundations that seem so bare and minimal. (And still others have just denied that we're free agents.) Nonetheless, I think that if there is to be any answer to your difficult question, it is going to be found by adopting at least a vaguely Kantian approach.

For one contemporary philosopher's more-than-vaguely Kantian approach, see David Velleman's "A Brief Introduction to Kantian Ethics" (available in this volume).

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