β. There is more to interest us in Aristotle’s determination of sense-perception (De Anima, II. 5), as to which I shall make some further quotations. Sense-perception is in general a potentiality (we should say a receptivity), but this potentiality is also activity; it is therefore not to be conceived as mere passivity. Passivity and activity pertain to one and the same, or passivity has two senses. “On the one hand a passivity is the destruction of one state by its opposite; on the other hand, it is a preservation of what is merely potential by means of what is actual.” The one case occurs in the acquisition of knowledge, which is a passivity in so far as a change takes place from one condition (ἕξις) into an opposite condition; but there is another passivity, in which something only potentially posited is maintained, therefore knowledge is knowing in an active sense (_supra_, p. 182). From this Aristotle concludes: “There is one change which is privative; and another which acts on the nature and the permanent energy (ἕξις). The first change in the subject of perception (αἰσθητικοῦ) is caused by that which produces the perception; but, once produced, the perception is possessed as knowledge (επιστήμη).” Because that which produces the change is different from the result, perception is passivity; but it is just as much spontaneity, “and sense-perception, like knowledge (θεωρεῖν), has to do with this aspect of activity. But the difference is, that what causes the perception is external. The cause of this is that perceptive activity is directed on the particular, while knowledge has as its object the universal; but the universal is, to a certain extent, in the soul itself as its substance. Everyone can therefore think when he will,” and for this very reason thought is free, “but perception does not depend on him, having the necessary condition that the object perceived be present.” The influence from without, as a passivity, comes therefore first; but there follows the activity of making this passive content one’s own. This is doubtless the correct point from which to view perception, whatever be the manner of further development preferred, subjective idealism, or any other way. For it is a matter of perfect indifference whether we find ourselves subjectively or objectively determined; in both there is contained the moment of passivity, by which the perception comes to pass. The monad of Leibnitz appears, it is true, to be an idea opposed to this, since every monad, every point of my finger, as atom or individual, is an entire universe, the whole of which develops in itself without reference to other monads. Here seems to be asserted the highest idealistic freedom, but it is of no avail to imagine that all in me develops out of me; for we must always recollect that what is thus developed in me is passive, and not free. With this moment of passivity Aristotle does not fall short of idealism; sensation is always in one aspect passive.