In this thesis, I investigate the question of whether moral requirements are categorical. I consider various attempts that have been made -by Immanuel Kant, John McDowell, Thomas Nagel, Philippa Foot, Alan Gewirth and David Gauthier- to establish that they are categorical. I conclude that each of these attempts fails; and, on the supposition that we cannot establish that moral requirements are categorical, I consider whether it follows that they are hypothetical. I reject the claim that this does follow. I accept that we cannot establish that moral requirements are categorical because we cannot establish that an agent has (whatever his particular inclinations) reasons for acting in accordance with the requirements of morality which take precedence over reasons he might have for acting otherwise. However, I claim that we can establish that they are nonhypothetical- that an agent has (whatever his particular inclinations) reasons to act in these ways. The claim that moral requirements are categorical is often thought to be a feature that marks them out as requirements of a special kind, distinguishing them from requirements of other kinds - for example, from those of prudence. I end by considering whether, if we think of moral requirements as merely non-hypothetical, we will have to give up the idea that they are speciaL I suggest that requirements of other kinds should be thought of as merely hypothetical; and conclude that in establishing that moral requirements are nonhypothetical, we can continue to think of them as speciaL