blocked to seeing the founded character of all sensory and intellective awareness, and to understanding these as possibilities of Being-in-the-world.1 On the contrary, he takes the Being of 'Dasein' (to whose basic constitution Being-in-the-world belongs) in the very same way as he takes the Being of the res extensa—namely, as substance.
But with these criticisms, have we not fobbed off on Descartes a task altogether beyond his horizon, and then gone on to 'demonstrate' that he has failed to solve it? If Descartes does not know the phenomenon of the world, and thus knows no such thing as within-the-world-ness, how can he identify the world itself with certain entities within-the-world and the Being which they possess?
In controversy over principles, one must not only attach oneself to theses which can be grasped doxographically; one must also derive one's orientation from the objective tendency of the problematic, even if it does not go beyond a rather ordinary way of taking things. In his doctrine of the res cogitans and the res extensa, Descartes not only wants to formulate the problem of 'the "I" and the world'; he claims to have solved it in a radical manner. His Meditations make this plain. (Sec especially Meditations I and VI.) By taking his basic ontological orientation from traditional sources and not subjecting it to positive criticism, he has made it impossible to lay bare any primordial ontological problematic of Dasein; this has inevitably obstructed his view of the phenomenon of the world, and has made it possible for the ontology of the 'world' to be compressed into that of certain entities within-the-world. The foregoing discussion should have proved this.
One might retort, however, that even if in point of fact both the problem of the world and the Being of the entities encountered environmentally as closest to us remain concealed, Descartes has still laid the basis for characterizing ontologically that entity within-the-world upon which, in its very Being, every other entity is founded—material Nature. This would be the fundamental stratum upon which all the other strata of actuality within-the-world are built up. The extended Thing as such would serve, in the first instance, as the ground for those definite characters which show themselves, to be sure, as qualities, but which 'at bottom' are quantitative modifications of the modes of the extensio itself. These  qualities, which are themselves reducible, would provide the footing for such specific qualities as "beautiful", "ugly", "in keeping", "not in
1 'Damit ist aber vollends der Weg dazu verlegt, gar auch noch den fundierten Charakter alles sinnlichen und verstandesmässigen Vernehmens zu sehen und sie als eine Möglichkeit des In-der-Welt-seins zu verstehen.' While we have construed the pronoun 'sie' as referring to the two kinds of awareness which have just been mentioned, it would be grammatically more plausible to interpret it as referring either to 'Dasein's ways of behaving' or to 'the idea of Being as permanent presence-at-hand'.