Physics

A, 2. 184b 15 — 185a 15.

It is necessary that the principle be either one or many, and if one, then either unmoved, as Parmenides and Melissus say, or moved, as the natural philosophers say, some claiming air is the first principle, others water; but if many, then either finite or infinite; and if finite and more than one, then either two, three, four, or some other number; and if infinite, then either as Democritus says, the genus being one but differing in shape, or differing in form, or even being contraries. Likewise, those seeking how many things there are also inquire into this; for they ask, regarding the first things from which beings exist, whether these are one or many, and if many, whether finite or infinite, so that they seek the principle and the element, whether it is one or many. Now, to investigate whether being is one and unmoved is not to investigate the science of nature; for just as there is no longer any argument for the geometer to have with someone who denies his principles, as this belongs either to a different science or one common to all, so too for the one who investigates principles; for there is no longer a principle if there is only one, and it is "one" in that way. For a principle is a principle of something or of some things. It is similar to consider whether one should discuss a position like that of Heraclitus, or if someone were to say that being is one man, or to solve a sophistical argument The text in brackets is considered an interpolation by some editors: "which both arguments possess, both that of Melissus and that of Parmenides; for they assume falsehoods and their arguments are not syllogistic; Melissus's argument is more crude and does not contain a difficulty, but once one absurdity is granted, the others follow; but this is not at all difficult.". Let it be assumed by us that things that exist by nature are either all or some moved; this is clear from induction. At the same time, it is not appropriate to solve every argument, but only those which are falsely demonstrated from principles; those that are not, one should not solve.