Countless pages have been written about Being and Time: books, essays, articles, introductions, even a "phenomenological commentary," but not—at least as far as we know—a companion piece, that is, texts that collect and interpret not only each of the 83 paragraphs that make up this work, but also enrich them with references to other books by Heidegger himself or with allusions to other thinkers, among whom Heraclitus, Plato, Aristotle, Descartes, Kant, Hegel, and others stand out. The peculiarity of this accompanying text is that it was written by the members of the Metaphysics Seminar—some of them academics from the Faculty itself or from other educational institutions—and is intended for and directed both to undergraduate and graduate students in philosophy, as well as to scholars of this work in general.