Above all, certain distinctions, which in the doctrine of the pure concepts have been seen to be without significance or importance, find their significance in the doctrine of the pseudoconcepts. We understand, for instance, how and why _identical_ concepts can be discussed; since, in the field of caprice, one and the same thing, or one and the same not-thing, can be defined in different ways and give rise to two or more concepts which, owing to the identity of their matter, are thus identical. The concept of a figure having three angles, or that of a figure having three sides, are identical concepts, alike applicable to the triangle; the concept of 3 x 4 and that of 6 x 2 are identical, since both are definitions of the number 12; the concept of a feline domestic animal and that of a domestic animal that eats mice are identical, both being definitions of the cat. It is likewise clear how and why _primary_ and _derived, simple_ and _compound_ concepts are discussed; for our arbitrary choice, by forming certain concepts and making use of these to form others, comes to posit the first as simple and primitive in relation to the second, which are, in their turn, to be considered as compound or secondary. [Sidenote: _The subordination and co-ordination of the empirical concepts._] We have already seen that the arbitrary concept differs from the pure concept in that, of necessity, it produces two forms by the two acts of empiricism and emptiness and thereby gives rise to two different types of formations, empirical and abstract concepts. Empirical concepts have this property, that in them unity is outside distinction and distinction outside unity. And it is natural: for if it were the case that these two determinations penetrated one another, the concepts would be, as we have already noted, not arbitrary, but necessary and true. If the distinction is placed outside the unity, every division that is given of it is, like the concepts themselves, arbitrary; and every enumeration is also arbitrary, because those concepts can be infinitely multiplied. In exchange for the rationally determined and completely unified distinctions of the pure concepts, the pseudoconcepts offer multiple groups, arbitrarily formed, and sometimes also unified in a single group, which embraces the entire field of the knowable, but in such a way as not to exclude an infinite number of other ways of apprehending it.