  Having completed what we might think of as the first phase of the existential analytic, Heidegger uses its results to launch an attack on one of the front-line representatives of the tradition, namely Descartes. This is the only worked-through example in Being and Time itself of what Heidegger calls the destruction (Destruktion) of the Western philosophical tradition, a process that was supposed to be a prominent theme in the ultimately unwritten second part of the text. The aim is to show that although the tradition takes theoretical knowledge to be primary, such knowledge (the prioritization of which is an aspect of the ‘onticization’ of Being mentioned earlier) presupposes the more fundamental openness to Being that Heidegger has identified as an essential characteristic of Dasein.