So far, however, we only stand on the threshold of Platonic love. The earthly passion, being itself a kind of generalisation, is our first step in the ascent to that highest stage of existence where wisdom and virtue and happiness are one—the good to which all other goods are related as means to an end. But love is not only an introduction to philosophy, it is a type of philosophy itself. Both are conditions intermediate between vacuity and fulfilment; desire being by its very nature dissatisfied, and vanishing at the instant that its object is attained. The philosopher is a lover of wisdom, and therefore not wise; and yet not wholly ignorant, for he knows that he knows nothing. Thus we seem to be thrown back on the standpoint of Plato’s earliest agnosticism. Nevertheless, if the _Symposium_ agrees nominally with the _Apologia_, in reality it marks a much more advanced point of speculation. The idea of what knowledge is has begun to assume a much clearer expression. We gather from various hints and suggestions that it is the perception of likeness; the very process of ascending generalisation typified by intellectual love. It is worthy of remark that in the Platonic Erôs we have the germ—or something more than the germ—of Aristotle’s whole metaphysical system.[135] According to the usual law of speculative evolution, what was subjective in the one becomes objective in the other. With Plato the passion for knowledge had been merely the guiding principle of a few chosen spirits. With Aristotle it is the living soul of Nature, the secret spring of movement, from the revolution of the outermost starry sphere to the decomposition and recomposition of our mutable terrestrial elements; and from these again through the whole scale of organic life, up to the moral culture of man and the search for an ideally-constituted state. What enables all these myriad movements to continue through eternity, returning ever in an unbroken circle on themselves, is the yearning of unformed matter—that is to say, of unrealised power—towards the absolute unchanging actuality, the self-thinking thought, unmoved, but moving every other form of existence by the desire to participate in its ineffable perfection. Born of the Hellenic enthusiasm for beauty, this wonderful conception subsequently became incorporated with the official teaching of Catholic theology. What had once been a theme for ribald merriment or for rhetorical ostentation among the golden youth of Athens, furnished the motive for his most transcendent meditations to the Angel of the Schools; but the fire which lurked under the dusty abstractions of Aquinas needed the touch of a poet and a lover before it could be rekindled into flame. The eyes of Beatrice completed what the dialectic of Plato had begun; and the hundred cantos of her adorer found their fitting close in the love that moves the sun and the other stars.