We must turn to moral naturalism for its main thesis. Moral naturalism maintains that all moral facts can be explained in a natural way. By this I mean that moral facts can be explained by physics, chemistry, and psychology. A more precise definition of moral naturalism would be achieved if we compare moral naturalism with moral non-naturalism. Moral non-naturalism is committed to the view that some moral facts are not constructed by nature (i.e. humans), but rather exist independent of nature and the world. This helps to understand moral naturalism since it would be the counter claim of moral non-naturalism. Since a working definition has been achieved, I want to focus in the remainder of my paper on moral naturalism’s ability to ground morality and its explanation of moral normativity.
Moral naturalism as I see it only has two ways of grounding morality. One method might be called the question begging way of determinism. The question begging way of determinism attempts to ground morality in determinism. In this way morality becomes a by-product of determinism. Thus to answer the question why something is morally wrong on this view is to answer because that is the way humans think. Notice this reply assumes the very thing in question that there is something morally wrong. To say that human psychology is determined to think in moral terms is to beg the question all together. For just because our cognitive faculties may tell us an action is morally wrong does not mean in fact it is. Hence, in a pejorative way I call the determinism grounding of morality question begging.
The other approach maybe referred to as the consensus thesis. The consensus thesis can be stated as morality being grounded upon the opinions of all people in a given society. This position can be better understood by an analogy which I call moral naturalism’s doctors.
Imagine there being in a foreign land a society of doctors. Suppose all the doctors do everyday is examine their health problems. Now consider the doctors giving each other prescriptions for their health problems. The parallel between the doctors and the moral naturalist consensus thesis can be drawn in that both examine how things are (i.e. health problems, or human behavior) and from these descriptions they make a prescription. In the case of the doctors, medicine is prescribed to make people be the way they should be—healthy. But in the case of the moral naturalist consensus thesis, human conduct is prescribed to make people be—moral. So both the doctors and moral naturalists end up making prescriptions of a different kind from descriptions of human behavior.
Though this story is not perfect we do see the difficulty of grounding morality on consensus. In the case of the doctors they already had training in perceiving health problems to make prescriptions, but in the case of the moral naturalists this is not so. In the moral naturalists view morality was contracted by the consensus. There was no morality or moral training prior to the contract. The difficulty with this is who is to say that one person’s opinion is any greater in force or significance than any others. Besides, there is no value between the majority and the minority views on morality unless it comes down to utility. But this too begs the question. Utility must be grounded as a principle for grounding morality in human consensus.