Lecture 1 — The things it pertains to natural science to consider

1 The science which has to do with nature clearly concerns itself for the most part with bodies and magnitudes and their properties and movements, but also with the principles of this sort of substance, as many as they may be. For of things constituted by nature some are bodies and magnitudes, some possess body and magnitude, and some are principles of things which possess these.

6. In this first book Aristotle begins for the first time to apply to bodies the things that were said about motion in a general way in the book of the Physics.

For that reason he first shows by way of introduction that it pertains to natural science to determine about bodies and magnitudes;

second he begins to carry out his proposal, at now a continuum (268a6).

With respect to the first he presents this argument: natural things are bodies and magnitudes and whatever pertains to these. But natural science is about natural things. Therefore, natural science consists in treating of bodies and magnitudes.

7. First therefore, he posits the conclusion, saying that the science which treats of nature seems to be for the most part (268a1) concerned with bodies and magnitudes, i.e., lines and surfaces. However, the natural philosopher considers these in a different way from the geometer. For the former treats of bodies insofar as they are mobile, and of surfaces and lines insofar as they are the boundaries of mobile bodies; the geometer, on the other hand, considers them insofar as they are measurable quantities. And because a science should consider not only subjects but also their passions, as is said in Post. Anal. I, he therefore adds that natural science is concerned with the passions and motions of the aforesaid—by passions meaning alterations and other consequent motions, with respect to which something is altered in the substance of a thing; and he adds, and motions, as though going from the particular to the general. Or perhaps by motions he specifically understands local motions, which are the more perfect in the genera of motions. Or by passions is meant the properties, and by motions the operations of natural things, which do not occur without motion. And because in every science principles must be considered, he adds that natural science is concerned with any and all the principles of the afore-mentioned substance, namely, mobile corporeal substance. By this we are given to understand that it pertains to natural science primarily to consider body insofar as it is in the genus of substance, for it is in this respect that it is the subject of motion; whereas it pertains to the geometer to consider it insofar as it is in the genus of quantity, for thus it is measured.

Since the minor premise is plain, namely, that natural science is concerned with natural things, he adds the major, saying that the reason why natural science is concerned with the aforementioned is that among things which are according to nature, some are bodies and magnitudes, e.g., stones and other inanimate things; and some have body and magnitude, as do plants and animals, whose principal part is the soul (hence they are what they are more with respect to soul than with respect to body); finally, some things are principles of things having body and magnitude—for example, the soul, and universally form, and matter. From this is clear why he said that the science of nature is for the most part concerned with bodies and magnitudes: for one part of this science is concerned with things having body and magnitude; it is also concerned with the principles of these; it is further concerned with some things which do not exist in nature but which some have attributed to bodies and magnitudes, namely, the void and the infinite.