Does rationalism rest upon reason alone?

This dissertation is a critique of rationalist views which hold that moral actions are both justified and motivated by reason alone. On some such views, this conjunction of rational motivation and justification gives some actions special status as, at once, rational, morally good, and autonomous. I will refer to this sort of view as autonomous rationalism. If morality is composed of requirements of rationality, then we must be able to explain through reason why we should act morally without appealing to any motivation or assumption other than our rationality. One way to do so is to argue that moral requirements are in some sense constitutive of rational agency. I argue that this is not ultimately plausible. The law of non-contradiction, for example, is taken to be a constitutive requirement of theoretical reason – one must be committed to it in order to engage in theoretical reasoning at all. Morality seems to be different. I argue that one can engage in practical reasoning, for example, without thereby being committed to moral principles. My dissertation begins by presenting historical background for autonomous rationalism and its critique. I develop an interpretation of certain aspects of Nietzsche’s criticism of morality that serve as background for the approach that I develop in later chapters. I then discuss Kant’s view, which is the historical source for autonomous rationalism. With this historical background in place, I turn to contemporary views. I discuss in detail the views of Korsgaard and Nagel who in different ways attempt to defend autonomous rationalism. Finally, I step away from the particulars of Kant’s, Korsgaard’s, and Nagel’s arguments that were the focus of the earlier chapters and discuss the prospects for the type of argument they are all, at a more abstract level, employing. They all justify moral requirements on the basis of a certain conception of ourselves that is, according to them, inescapable given our rational agency. Although I think that the prospects for justifying some rational requirements in such a way are bright, I argue that it is unlikely that moral requirements in particular could be justified in this way.Philosoph