The paper offers a reflection on the life and work of Guido Calogero (Rome, December 4, 1904 – Rome, April 17, 1986), undoubtedly one of the most engaged and active intellectuals of twentieth-century Italy, thanks to his civic, political, and philosophical commitment. In addition to highlighting the key moments of his career as a scholar and political figure, the focus will be on his philosophy—commonly known as the "philosophy of dialogue"—and on the theoretical implications of such an approach: the constant presence and self-awareness of the individual, the human openness to otherness and the conscious intention to understand it, the idea of secularism as the foundation of his ethics, the uselessness of metaphysics as a guide for human choices, and the autonomy of ethics from logic. Finally, special attention will be given to his deep engagement with ancient philosophy and classical thinkers—Socrates above all—whose example leads Calogero to transcend the “philosophy of knowledge” and resolve it within ethics, that is, precisely, in a “philosophy of dialogue”.