Page:Theory of Mind of Roger Bacon.djvu/13

 the same uncertainty as Aristotle. But all the more do we find his efforts directed toward clarifying the second and third. The vantage ground from which he makes his further development is that of Optics; an advantage which he owes especially to Ptolemy and Alhazen. We shall later see how this element is combined with the Aristotelian conception. Let us now see how closely Bacon follows Aristotle for the general setting of his theory.

His point of departure is along the same broad lines as Aristotle’s. After Matter and Form and Privation, he says, the natural Philosopher has two fundamental factors to investigate; these are motion with respect to Place, and motion with respect to Form. It is the latter rather than the former in which he is interested; for it has to do with qualitative change, and includes alteration, generation-dissolution, and increase-diminution. Now while the last of these three is usually involved in the first two, yet strictly this sort of change is not effected through the Species, which never adds to the quantity. His theory is therefore really directed to alteration and generation-dissolution. For alteration has to do, not with quantity as such, but with the Form that is to be designed or released in this quantity. And alteration is of two kinds, complete and incomplete. In the one case, we have an entire transformation whereby the very nature of the Patient is replaced; loosely speaking, there is a certain generation of species here. And in the other case we have the kind of alteration (of the senses, for example, and the rest) which is effected through the Species; this is the sense in which he means to use the word. With this, it will be observed, is given the distinction between generation-dissolution and alteration, in the Aristotelian sense of change in substance and change in accidents. Bacon suggests that his theory is meant to be applied only to the latter, but he is obviously uncertain; and in point of fact he abides by no hard and fast distinction.