"The Justification of the 'Supreme Good' in Kant" is an in-depth analysis of the central concept of the Supreme Good in the philosophy of Immanuel Kant. The author, Ernesto Aguilar, aims to develop a systematic understanding of this concept and to justify its philosophical legitimacy. The book highlights the fundamental role of the Supreme Good in Kantian ethics and argues that it possesses its own systematic unity, which aligns with the logical coherence of Kant's practical philosophy. By examining Kant's texts and discussing the components of happiness and virtue, the significance of the Supreme Good as a necessary and universal element of ethics is emphasized. Furthermore, an innovative approach is presented that introduces the idea of a fourth postulate, divine grace, and discusses the possibility of an indirect, sensitive representation of the Supreme Good through imagination. Thus, the work not only offers a critical engagement with existing interpretations but also provides new perspectives on Kant's ethical theory.