Martin Heidegger (1889–1976) was a tremendously original, highly influential, and troublesome philosopher. What makes his work troublesome is not only conceptual difficulty and a deliberate practice of translating the familiar into the unfamiliar, but also his never clearly repudiated attempt to influence the Nazi movement in Germany. He seems to have been a cultural and linguistic chauvinist who rejected pseudo-biological racism, but nonetheless put hopes in an “inner truth and greatness” of National Socialism as an alternative to American and Soviet materialism. This identification puts a dark cloud over the interpretation of his writing, which was, however, generally very far removed from politics. The question is, how much it is possible to detach his work from a stance that seems worse than one of mere bad judgment.

A serious and innovative reader of Aristotle who also developed thought-provoking readings of Plato, Kant, Hegel, and Nietzsche, Heidegger combined a sympathetic but critical take on Husserl’s phenomenology with an interest in the hermeneutics of Wilhem Dilthey. Widely read as an “existentialist”, he sharply repudiated Sartre’s appropriation of his work. In his later works, he approached philosophy as a kind of poetic meditation.

His most famous thesis was that Western thought largely lost its way from Plato onward, neglecting the question of the meaning of Being in favor of preoccupation with things. While he made good points about the preconceptions involved in our ordinary encounters with things, I think he too sharply rejected “ontic” engagement with empirical, factual concerns in favor of a purified ontology. He also promoted a valorization of what I would call the pre-philosophical thought of the pre-Socratics Heraclitus and Parmenides. I think Plato and especially Aristotle represented a gigantic leap forward from this.

Some of Heidegger’s very early work was on the medieval theologian Duns Scotus, who seems to have originated the standard notion of ontology later promoted by Wolff and others. In sharp contrast to the tradition stemming from Scotus, Heidegger argued that Being is not the most generic concept, and wanted to emphasize a “Being of beings” in contrast to their factual, empirical presentation. He did not follow the path of Aquinas in identifying pure Being with God, either, and Aquinas probably would have rejected his talk of the Being of beings.

I think his most important contribution was an emphasis on what he called “being-in-the-world” as a way of overcoming the dichotomy of subject and object. His associated critique of Cartesian subjectivity has been highly influential. In later works, he also recommended putting difference before identity, and relations before things. Although the way he expounded these notions was quite original, I prefer to emphasize their roots in Aristotle, Kant, and Hegel.