This book presents a synthesizing interpretation of Kant’s idea of practical metaphysics, also referred to as metaphysics of the good will. Kant elaborates this idea primarily in his Critique of Practical Reason, however, it is also included in other texts on theoretical and practical philosophy. Although the expressions "metaphysics of the good will" and "practical metaphysics" are not used in any of the texts verbatim, they express the idea, which Kant elaborated with great effort, that it is worth striving to understand it adequately. It may be summarized by saying that should something like metaphysics be possible at all, it may only be through reflected, responsibly approached practice.