But if one considers that this nature is nothing in itself but a sum of appearances, hence not a thing in itself but merely a multitude of representations of the mind, then one will not be astonished to see that unity on account of which alone it can be called object a of all possible experience,.e., nature, solely in the radical faculty of all our cognition, namely, transcendental apperception; and for that very reason we can cognize this unity a priori, hence also as necessary, which we would certainly have to abandon if it were given in itself independently of the primary sources of our thinking.