De causis curatricibus Theses Progymnasticae

XXII.
Now, let us determine the efficient cause or principle of all these effects: since, in what subject and why these things happen is now clearly evident.

XXIII.
It is certain that all material bodies considered in themselves, whatever they may be, do not move themselves (especially with artificial and ordered motions, as appears here), but are moved. For although nothing can be done in natural things without matter, it is rightly taught by the philosophers that it is only passive and not active, and thus is the effective principle of no action. If, therefore, they are moved (as they certainly are moved, each according to the condition of its kind), it is necessary that they be moved by either an extrinsic or intrinsic cause. For without a cause, nothing can be effected in the Nature of things.

XXIV.
That the enumerated motions in the human body do not arise from an extrinsic cause is evident, first, because they happen spontaneously, and without any cause present that might seem capable of effecting such things. Therefore, it is consistent that they proceed from an intrinsic one.

XXV.
But in establishing this, the opinions of the schools vary not a little. For the common crowd of doctors speaks of it one way, more exquisite philosophers another, and physicians yet another. The crowd calls it "Nature" indefinitely; so that as often as the reason for effects in natural things is sought, it sounds nothing other than "Nature," while ignorant of what and of what kind it is. As Lactantius rightly said: "The name of Nature was introduced out of ignorance of things." And Galen, in his book on the formation of the fetus: "It is the custom of the common people and the ignorant to refer the works of things to Nature without any other more open explanation."

XXVI.
Philosophers and physicians define the matter a little more distinctly and expressly, when they consider in the investigation of things not those common and indeterminate reasons, but the proximate and proper ones.

XXVII.
According to the philosophers, and the Peripatetics especially, in composite substances or mixed bodies, whatever have been created by God in this elementary world, and are still generated by His order and command, two substantial parts are present: Matter and a certain Faculty. Matter is indeed concreted from the four elements and tempered by their mutual actions and passions; but the Faculty is the force and power in matter producing certain and peculiar motions and actions.