Introduction to Metaphysics (German: Einführung in die Metaphysik) is a revised and edited 1935 lecture course by Martin Heidegger first published in 1953. The work is notable for a discussion of the Presocratics and for illustrating Heidegger's supposed "Kehre," or turn in thought beginning in the 1930s—as well as for its mention of the "inner greatness" of Nazism. Heidegger suggested the work relates to the unwritten "second half" of his 1927 magnum opus Being and Time. Source: Wikipedia (en)