Philosophy Ph.D. Dissertations


Non-natural Moral Properties: Sui Generis or Supernatural?

Date of Award


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Philosophy, Applied

First Advisor

Christian Coons (Advisor)

Second Advisor

Michael Weber (Committee Member)

Third Advisor

Sara Worley (Committee Member)

Fourth Advisor

Alfred DeMaris (Other)


If we grant that some moral claims are true, what is it that makes them true? Throughout the vast majority of history, it was believed that God was the source of morality. But the twentieth century saw a shift in ethics. Influenced by logical positivism and a broadly naturalistic worldview, scholars sought to develop a theory of ethics that did not depend on God's existence. One leading approach was moral naturalism, the view that moral properties are natural and thus can be investigated by scientific methods. But this view was plagued with problems, leading many to conclude that moral and natural facts were just too different to be one and the same.

Having rejected a divine conception of ethics and moral naturalism, some scholars turned to moral non-naturalism - the view that moral properties are not natural. One particular form of moral non-naturalism entails that moral properties are sui generis. I call this view Moorean realism.

The current trend suggests that Moorean realism is preferable to divine command theory, a competing form of moral non-naturalism wherein moral properties are reducible to supernatural properties. But, as far as the salient objections go, divine command theory is at least as plausible as Moorean realism. Indeed, if we look closely at the traditional versions of these views and the common objections to them, divine command theory offers compelling responses and Moorean realism has a difficult time meeting many of these challenges. In chapter one, I argue that divine command theory is as plausible as Moorean realism.

In chapter two, I consider the viability of a non-traditional form of Moorean realism - the view that moral truths are conceptual truths. I argue that the thesis that moral truths are conceptual faces a serious dilemma which renders the view in question implausible.

In chapter three, I argue that it is indeed the traditional divine command theory and not the intriguing deflationary one whereby God need not exist, that deserves the revival.

If moral properties are not natural, it is very plausible that they are supernatural. Divine command theory - the traditional non-deflationary form - is alive and well.