De Rervm Natvra Constantivm Scientia, Principiis Et Affectionibvs Commvnibvs, Dispvtatio

first, because it proceeds in evincing effects through demonstration, from causes that cannot fail. Second, because from causes which can be impeded, it collects effects, not that they always happen, but for the most part, or with a condition posited, and impediments removed. Third, because in concluding affections about things that perish, it acts only about them for that time in which it is truly said that they are; some say the same thing, that Physics abstracts from generation and corruption.

VI. Consequent to this is that, although it deals with corruptible things, it nonetheless deals with things that are perpetually true; for this is what is usually said: that science deals with incorruptible and perpetual things; [and] that the cognition which is practiced as science at any time is always true and conformable to the thing toward which it is directed. Although some may dissent from this interpretation and may wish that the essences of things enjoy perpetuity in reality, they incorrectly accept that the essences of those things which in reality differ from GOD are perpetual; since, unless produced, they cannot obtain the reason of essence; and the same judgment must be rendered concerning that which others interpret as Physics dealing with incorruptible things, that is, which never arise nor perish in act; for Physics discusses and argues about these same individual things, which are subject to changes, through a concept or universal cognition.

VII. Having posited that natural philosophy is embraced by the definition of science, we shall hold the same reason in explaining its unity as in declaring the unity of the other sciences; namely, that one [science] is constituted and distinguished from others according to the unity and diversity which is among the acts of which it causes the propensity, just as a habit [does]; for as habits, so the sciences are referred to determined acts or to exercising those of a certain kind, and they are brought forth with determination by acts of the same kind. Since this is the cause that habits are distinguished and constituted among themselves with respect to acts, the same will cause the sciences to receive both their essence and their difference from them.

IIX. With this established, two paths occur, to either of which we can hold: either that we say the acts of the intellect are contained in the same species