This text examines the bearing of Heidegger's philosophy on his original commitment to Nazism and on his later inability to face up to the implications of that allegiance. The author focuses on Heidegger's connection with other philosophers, most notably Karl Jaspers.

After examining Heidegger's relation to Husserl in volume three, Robert Denoon Cumming moves on in this volume to Heidegger's relation to Karl Jaspers, an old friend on whom Heidegger turned his back when Hitler came to power, and who discredited Heidegger in the denazification process which followed World War II. The issues between them were not merely personal, but concern the philosophical relevance of the personal, a stance which Heidegger denied and on which Jaspers insisted.

In this setting, Cumming interprets Heidegger's first postwar essay, the "Letter on Humanism," as explaining how Heidegger became, as he put it, "more emancipated from the contemporary," and able to disregard his earlier Nazi allegiance. Since the "Letter" is also an attack on Sartre, who remained committed to the contemporary, their confrontation provides Cumming with a concluding problem for his four volumes-how philosophies would determine their location in history.