INTRODUCTION

In addition to recognizing a moral contrast between lying and telling the truth, philosophers have sometimes postulated a modal asymmetry. Perhaps the most famous example occurs in Kant's ethical theory, where the moral contrast is said to derive from a modal difference. For Kant, truthfulness is right and lying is wrong because truthfulness can be universalized, whereas lying cannot. In his well-known discussion of promise-keeping in the Groundwork of the Metaphysics of Morals, Kant describes a person who needs money and is deciding whether to borrow. The question is whether it would be permissible to promise to pay back the money if you have no intention of doing so. Kant argues that morality requires that you not lie – you can make the promise only if you intend to keep it:

Kant is saying that promise-keeping could not exist as an institution, if everyone who made promises did so with the intention of breaking them.