Abstract
This paper attempts a deduction of Kant's concept of the highest good: that is, it attempts to prove, in accordance with Dieter Henrich.s interpretation of the notion of deduction, that the highest good is an end that is also a duty. It does this by appealing to features of practical reason that make up the legitimating facts that serve as the premises that any deduction must possess. According to Kant, the highest good consists of happiness, virtue, and relations of proportionality and causation between happiness and virtue, such that happiness is proportional to and caused by virtue. I argue, by drawing on accepted Kantian notions, that Kant had compelling reasons for concluding that the highest good is in fact an end that is also a duty. If correct, then this argument provides the deduction promisedin my title.