This dissertation explores some objections to natural law theory- many of which are also leveled against contemporary naturalism. Despite the way the natural law tradition has fallen into disrepute in much of the American academy, this dissertation defends a classical Thomistic approach to natural law from some modern and contemporary criticisms. It begins with a brief explanation of the theory of natural law that will be defended from these contemporary objections. Chapter three examines G.E. Moore and David Hume's classical problems (...) posed to natural law, along with some contemporary defenders of Moore's position. These arguments are purported to undermine using human nature as a basis for ethics. Chapter four considers how moral relativism, especially the form given by Gilbert Harmon and David Wong, offers a unique challenge to natural law that must be answered and one that seems to undermine any ethical theory than any account relying on human nature. Chapter five explores the relation between neo-naturalism and natural law. Although neo-naturalism is a position often thought of as opposed to natural law, the two share many similarities in the positions they oppose. The last chapter examines how natural law reasoning is used in making medical decisions. The overarching thesis is that, insofar as natural law is coherent and answers many major criticisms, the proposal to reexamine this ethical theory stands as viable. (shrink)