the principle of its form in itself, it does not make itself an axe, nor does its form, its Notion, in itself constitute its substance, as its activity is not through itself. “If, for instance, the eye were in itself a living thing, vision would be its soul, for vision is the reality which expresses the Notion of the eye. But the eye, as such, is only the material instrument of vision, for if vision were lost, the eye would be an eye only in name, like an eye of stone or a painted eye.” Thus to the question, What is the substance of the eye? Aristotle answers: Are the nerves, humours, tissues, its substance? On the contrary, sight itself is its substance, these material substances are only an empty name. “As this is the case in the part, so it also holds good of the body as a whole. The potentiality of life is not in any such thing as has lost its soul, but in that which still possesses it. The seed or the fruit is such and such a body potentially. Like hewing and seeing,” in the axe and the eye, “waking” in general “is activity; but the corporeal is only potentiality. But as the” living “eye is both vision and the eyeball” (the two being connected as actuality and potentiality), “so also are soul and body the living animal, the two are not to be separated. But it is not yet clear whether the soul is the activity of the body in the same way as the steersman is of the ship.” That the active form is the true substance, while matter is so only potentially, is a true speculative Notion. As settling the question asked in the above-mentioned metaphor, we may quote what Aristotle says later (De Anima, II. 4): “As the principle of motion and as end (οὗ ἕνεκα), and as substance of living bodies, the soul is the cause. For substance is to all objects the cause of their existence, but life is the existence of the living, and its cause and principle is the soul; and further, its energy is the existing Notion of what has potential existence. The soul is cause also as end,” that is, as self-determining universality, “for nature, like thought, acts for the sake of an object, which object is its end, but in living beings this is soul. All the parts of the body are thus the organs of the soul, and hence exist for its sake.” In like manner Aristotle shows that the soul is the cause of motion.