I will consider how the notion of incommensurability, as championed by Parfit (Reasons and persons, 1984), Griffin (Well-being: its meaning, measurement and importance, 1986), Chang (Ethics 112:659–688, 2002), and Hare (Philos Perspect 23:165–176, 2009), might affect both the argument from slight pain (which suggests God’s non-existence can be inferred from the merest stubbing of one’s toe) and Leibniz’s reply to this argument. I conclude that the notion of incommensurability may ultimately strengthen Leibniz’s general position.

My dissertation is a systematic defense of the claim that what it is to be rational is to correctly respond to the reasons you possess. The dissertation is split into two parts, each consisting of three chapters. In Part I--Coherence, Possession, and Correctly Responding--I argue that my view has important advantages over popular views in metaethics that tie rationality to coherence (ch. 2), defend a novel view of what it is to possess a reason (ch. 3), and defend a novel (...) view about what it is to act and hold attitudes for normative reasons (ch. 4). In Part II--Foundationalism, Deception, and The Importance of Being Rational--I argue that foundationalists about epistemic rationality should think that the foundational beliefs are held for sufficient reasons (ch. 5), argue that my view solves the New Evil Demon problem for externalism (and solves a related and underapprieciated problem) (ch. 6), and argue that my view can vindicate the thought that we ought to be rational (ch. 7). (shrink)