Abstract

The paper addresses O'Neill's view that her version of Kant's Categorical Imperative, namely, the requirement of followability (RF), marks the supreme principle of reason; it takes issue with her claim that RF commits us to Kantian constructivism in practical philosophy. The paper distinguishes between two readings of RF: on a weak reading, RF ranges over all (practical) reasoning but does not commit to constructivism, and on a strong version RF commits to constructivism but fails to meet its own test, and so is self-defeating. The paper argues that RF, if understood strongly, depends for its reasonableness on reasons that cannot coherently be required to meet RF, so that RF cannot be the supreme principle of reason. The paper considers several responses to this problem in order to suggest that RF depends for its reasonableness on perfectionist considerations.