To carry our inquiry further, we must take up again a problem that has impelled the thinking of a whole series of contemporary philosophers to enter upon strange paths. The insight that concepts and other logical structures are not mental realities has led these philosophers to ascribe a special kind of "being" to them, and like Plato to counterpose the realm of real being and the realm of ideal being as two quite different and separate spheres. In acts of thought, however, the two realms must somehow come into connection or communication with one another; and thus the problem consists precisely in giving an account of how this is possible. The metaphorical, Platonist solution, according to which ideas are simply "intuited" by our mind, no longer satisfies us today.