Heidegger’s critique of Sartre’s misreading of Being and Time is imparted in “Letter on Humanism” (1946), as a direct response to a letter from one of Sartre’s followers, Jean Braufret. Heidegger’s “Letter” distances himself from Sartre’s existentialism philosophically and, more importantly, questions humanism in particular because, according to Heidegger, “every humanism is either grounded in a metaphysics or is itself made to be the ground of one” (225). Heidegger criticizes Sartre’s pronouncement of existence precedes essence for not escaping metaphysics—if we are to assume that Sartre is as interested in destrukting metaphysics as Heidegger (though I doubt Sartre’s intentions are Heideggerian)—even if it attempts to reverse Platonic metaphysics by offering a reversal of the essence–existence metaphysical statement. To this extent, Heidegger contends that “the reversal of a metaphysical statement remains a metaphysical statement [and] with it, [Sartre] stays with metaphysics in oblivion of the truth of Being” (232). Not only does Heidegger suggest that Sartre’s handling of metaphysics “happens clumsily enough,” but he argues that Being and Time is in opposition humanism (233). To this end, Heidegger suggests that:
…this opposition does not mean that such thinking aligns itself against the humane and advocates the inhuman, that it promotes the inhumane and deprecates the dignity of man. Humanism is opposed because it does not set the humanitas of man high enough. Of course, the essential worth of man does not consist in his being the substance of beings, as the ‘Subject’ among them… (233-234).
Here, Heidegger’s explanation of his opposition is riddled with contradictions, each of which must be addressed individually before attempting to construct what it is about humanism he actually opposes. To be sure, this “opposition” is undoubtedly aligned with a kind of meta-metaphysical idea that is not humanism—that is, Sartre’s humanism, and more specifically, Sartre’s existence precedes essence. Yet, even though Heidegger opposes Sartrean humanism, he makes concessions, which seem to serve the purpose of suggesting that he does agree with some aspects of Sartre’s overall conceptualization of humanism—for Heidegger, to be “against the humane” or advocate “the inhuman” seems unimaginable, and any promotion of “the inhumane” and deprecation of the “dignity of man” become unethical non-negotiables. To this end, Heidegger is certainly on board with Sartrean humanism, but only up to a point, and this point of diversion is very important to how Heidegger chooses to define humanism.
Clearly, Heidegger is careful to argue that his “opposition,” as exemplified in Being and Time, is not “align[ing] itself against the humane and advocates the inhuman,” by implying that he is just as much concerned with “the human” (and the humane) as Sartre. The centering of “the human” is, in particular, a kind of metaphysics that Heidegger is ultimately unwilling to completely eliminate—even if Heidegger disagrees with Sartre’s existence precedes essence, his concern with the relationship between “existence” and “essence” remains a significant strand in his “opposition” to Sartrean humanism. To what exactly is Heidegger in “opposition”?
Such a question does not yield a straightforward answer, because Heidegger’s “opposition” to Sartre seems muddled and contradictory—but, perhaps, not quite as muddled as Heidegger’s opposition to Platonic thought.