_b._ In the Sophist Plato investigated the pure Notions or Ideas of movement and rest, self-identity and other-being, Being and non-being. He here proves, as against Parmenides, that non-being is, and likewise that the simple self-identical partakes of other-being, and unity of multiplicity. He says of the Sophists that they never get beyond non-being, and he also refutes their whole ground-principle, which is non-being, feeling, and the many. Plato has thus so determined the true universal, that he makes it the unity of, for example, the one and many, Being and non-being; but at the same time he has avoided, or it was his endeavour to avoid, the double meaning which lies in our talk of the unity of Being and nothing, &c. For in this expression we emphasize the unity, and then the difference disappears, just as if we merely abstracted from it. Plato tried, however, to preserve the difference likewise. The Sophist is a further development of Being and non-being, both of which are applicable to all things; for because things are different, the one being the other of the other, the determination of the negative is present. First of all, however, Plato expresses in the Sophist a clearer consciousness of Ideas as abstract universalities, and his conviction that this point of view could not endure, because it was opposed to the unity of the Idea with itself. Plato thus first refutes what is sensuous, and then even the Ideas themselves. The first of these points of view is what is later on called materialism, which makes the corporeal alone to be the substantial, admitting nothing to have reality excepting what can be laid hold of by the hand, such as rocks and oaks. “Let us,” says Plato, in the second place, “proceed to the other, to the friends of Ideas.” Their belief is that the substantial is incorporeal, intellectual, and they separate from it the region of Becoming, of change, into which the sensuous falls, while the universal is for itself. These represent Ideas as immovable, and neither active nor passive. Plato asserts, as against this, that movement, life, soul, and thought, cannot be denied to true Being (παντελῶς ὄντι), and that the holy reason (ἄγιον νοῦν) can be nowhere, and in nothing that is unmoved.[36] Plato thus has a clear consciousness of having got further than Parmenides when he says:— “Keep your mind from this way of inquiry, For never will you show that non-being is.” Plato says that Being in anyone partakes both of Being and non-being; but what thus participates is different both from Being and non-being as such.[37]