Abstract

This dissertation investigates the problems of theoretical disagreement and incommensurability common to ethics and philosophy of science. Incommensurability theses in both philosophical genres purportedly undermine practical reason, theory evaluation and rational choice because incommensurability has been interpreted to mean incomparability. If two or more rival conceptual schemes are incommensurable, it is argued, then it is not possible to determine which is theoretically superior. Lacking a single unified method of theory evaluation and choice, the claim that one conceptual scheme is superior to another can only be justified by an appeal to theoretical standards internal to some larger methodological framework. Thus, incommensurable conceptual schemes appears to generate epistemological relativism, according to which rational belief and justification are relative to some conceptual scheme. ;I investigate two versions of the incommensurability thesis in ethics, one concerned with comparing values and another with comparing rival and incompatible large-scale moral schemes, in order to uncover which versions of the incommensurability thesis in ethics entail moral relativism. The first version does not entail relativism by itself. Elizabeth Anderson holds that incommensurable values do not pose a problem for practical reason because we are ultimately able to rank incommensurable values ordinally. I argue that this version of the thesis is problematic because the very notion of incommensurability employed is incoherent. The second version, defended by Alasdair MacIntyre, does generate problems for practical reason. He claims that there are no objective standards available for adjudicating disagreements between incommensurable moral views. ;I argue that MacIntyre's early analysis of moral incommensurability borrows from Thomas Kuhn's analysis of the problem in science and therefore runs into similar problems relating to epistemological relativism. In a later analysis, however, MacIntyre appears more optimistic about the possibility that theoretical disagreement in ethics is resolvable. He details when it is rational to reject one moral scheme for another, but I argue that he has not succeeded in circumventing the charge of moral relativism. I show how comparing rival conceptual schemes according to theoretical virtues like scope, consistency, and problem-solving ability, cannot demonstrate that one scheme is true, but only superior in that specific regard.