quod sit res existens, quia hoc solum per se nos non afficit ...".xvi 'Being' itself does not 'affect' us, and therefore cannot be perceived. 'Being is not a Real predicate,' says Kant,1 who is merely repeating Descartes' principle. Thus the possibility of a pure problematic of Being gets renounced in principle, and a way is sought for arriving at those definite characteristics of substance which we have designated above. Because 'Being' is not in fact accessible as an entity, it is expressed through attributes-definite characteristics of the entities under consideration, characteristics which themselves are.2 Being is not expressed through just a n y such characteristics, but rather through those satisfying in the purest manner that meaning of "Being" and "substantiality", which has still been tacitly presupposed. To the substantia finita as res corporea, what must primarily be 'assigned' ["Zuweisung"] is the extensio. "Quin et facilius intelligimus substantiam extensam, vel substantiam cogitantem, quam substantiam solam, omisso eo quod cogitet vel sit extensa ";xvii for substantiality is detachable ratione tantum; it is not detachable realiter, nor can we come across it in the way in which we come across those entities themselves which are substantially.
Thus the ontological grounds for defining the 'world' as res extensa have been made plain : they lie in the idea of substantiality, which not only remains unclarified in the meaning of its Being, but gets passed off as something incapable of clarification, and gets represented indirectly by way of whatever substantial property belongs most pre-eminently to the particular substance. Moreover, in this way of defining a substance through some substantial entity, lies the reason why the term "substance" is used in two ways. What is here intended is substantiality; and it getc; understood in terms of a characteristic of substance—a characteristic which is itself an entity.3 Because something ontical is made to underlie the ontological, the expression "substantia" functions sometimes with a signification which is ontological, sometimes with one which is ontical, but mostly with one which is hazily ontico-ontological. Behind this slight difference of signification, however, there lies hidden a failure to master the basic problem of Being. To treat this adequately, we must 'track down' the equivocations in the right way. He who attempts this sort of thing does not just 'busy himself' with 'merely verbal significations' ; he must venture forward into the most primordial problematic of the 'things  themselves' to get such 'nuances' straightened out.
1 Immanuel Kant, Critique of Pure Reason, Transcendental Dialectic, Book II, chapter III, Section 4.
2 '... seiende Bestimmtheiten des betreffenden Seienden ...'
3 '... aus einer seienden Beschaffenheit der Substanz.'