In traversing the expanse that leads from the implacable rigour of logical-rational explanation to the empathetic-intuitive understanding of Being, Heidegger not only outlines a speculative and historiographic itinerary within the confines of modern philosophy, but he also constructs a model of cosmological interpretation with which contemporary theory necessarily has to grapple. His profound excavation around the forms of reason enables Heidegger to come up with a philosophical hybrid, which is all the more disquieting in that it proves to be able to undermine the methodological certainty emanating from the causalistic version of the principle of reason. The image of the hybrid helps to clarify the nature of Heidegger's result: it is rooted in the ground of tradition, deconstructing it and pushing it forward into the abyss of Being, into that abyss that Kant had glimpsed but from which he drew back in horror. This result therefore absorbs metaphysics and reshapes it, taking away its representative and logical content, and even creating an opposing front, another philosophical horizon. We may imagine this process of genetic mutation by means of a metaphor drawn from the human organism. The organ par excellence where reason resides is the brain, or in a broad sense the intellect. Ever since Greek times voûs has been considered the centre of mental activity and the place where thought is rationally co-ordinated.