Book 3
9
Further, in all other cases too, even in such as admit of demonstration, we consider that we know a particular thing when we know what it is (e.g. what is the squaring of a rectangle? answer, the finding of a mean proportional to its sides; and similarly in other instances); but in the case of generations and actions and all kinds of change, when we know the source of motion.
10
This is distinct from and opposite to the end . Hence it might be supposed that the study of each of these causes pertained to a different science.See Aristot. Met. 4.1
10
(2.) Again, with respect to the demonstrative principles as well, it may be disputed whether they too are the objects of one sciencesc. the science which studies the four causes. or of several.Cf. Aristot. Met. 3.1.5.
11
By demonstrative I mean the axioms from which all demonstration proceeds, e.g. everything must be either affirmed or denied, and it is impossible at once to be and not to be, and all other such premisses. Is there one science both of these principles and of substance, or two distinct sciences? and if there is not one, which of the two should we consider to be the one which we are now seeking?
12
It is not probable that both subjects belong to one science; for why should the claim to understand these principles be peculiar to geometry rather than to any other science? Then if it pertains equally to any science, and yet cannot pertain to all, comprehension of these principles is no more peculiar to the science which investigates substances than to any other science.
13
Besides, in what sense can there in be a science of these principles? We know already just what each of them is; at any rate other sciences employ them as being known to us.sc. and so there can be no science which defines them. If, however there is a demonstrative science of them, there will have to be some underlying genus, and some of the principles will be derived from axioms, and others will be unproved
