Between ‘Indubitably Certain’ and ‘Quite Detrimental’ to Philosophy: Kant on the Guise of the Good Thesis

Abstract Kant clearly endorses some version of the ‘old formula of the schools’, according to which all volition is sub ratione boni . There has been a debate whether he holds this only for morally good actions. I argue that a closer look at the distinction between the good and the agreeable does not support this conclusion. Considering Kant’s account of the detrimental and the correct use of this thesis, I argue that rational beings always will sub ratione boni , even when they act immorally, because they act on principles. I argue that Kant’s accounts of self-love and self-conceit support this view.