Martin Heidegger exercised, and continues to exercise, a deep fascination and considerable influence over generations of students and philosophers. Between 1909 and 1911, Heidegger studied theology and philosophy at the Department of Philosophy at the University of Freiburg in preparation for the archdiocesan priesthood. In the very first sentence of the so-called 'Natorp Report', Heidegger describes his investigations as a contribution 'to the history of ontology and logic'. Heidegger describes the unity of factical life, or of the three existentials, as 'concern', or 'care'. Soon after the publication of Being and Time, Heidegger's thought began to shift from a transcendental-horizonal conception of the meaning of being, in which being temporalizes itself in the ekstatic temporality of Dasein, to what we could call an aletheic-ekstatic conception of the truth of being, in which Dasein finds its stance and to which it co-responds.