Since, however, it is necessary that motion should always be, and not fail, it is necessary that there should be something perpetual which first moves, whether there be one or many such natures; and which first moves being immoveable. That each of those things therefore, which are immoveable indeed, but move, is perpetual, does not pertain to the present enquiry. But that it is necessary there should be something, which is itself always imtnoveable indeed, is void of all external mutation, both simply and according to accident, and is motive of another, will be evident to those who thus consider the affair. But let it happen, if some one is disposed to admit it, in certain things, that they will sometimes be, and sometimes not, without generation and corruption; for, perhaps, it is necessary, that if any thing without parts at one time is, and at another is not, every thing of this kind should at one time be, and at another time not be, without mutation; and that of principles which are immoveable indeed but motive, it may also be possible that some of them may at one time be, and at another not; but it is not possible that all should be of this kind. For it is evident, that there is a certain cause to things, which move themselves, of their existing sometimes, and sometimes not; forit is necessary that every thing which itself moves itself, should have magnitude, if nothing without parts is moved. But there is no necessity that the nature which moves should have magnitude, as is evident from what has been said. Hence, one of those natures which are indeed immoveable, but which do not always exist, is the cause why some things are generated, and others corrupted, and this continually; nor yet any one of those which always indeed move these, but are themselves moved by others; for neither each, nor all of these, is the cause of perpetuity and continuity; since for a thing thus to subsist is perpetual, and from necessity; but all these are infinite; and all of them do not subsist at once. It is evident, therefore, that though there should be ten thousand principles which are immoveable indeed, but move; and many of those things which move themselves ahould be corrupted, and others be generated, and this thing being immoveable should move that, and another thing this; nevertheless there is something which comprehends or contains, and this besides particulars; which is indeed the cause why some things are, and others are not, and is the cause of continued mutation. And this indeed is the cause to these; but these are the causes of motion to others. If, therefore, motion is perpetual, the first mover also will be perpetual, if it is one, but if there be many first movers, there will be many perpetual movers. But it is necessary to think that there is rather one than many, and finite rather than infinite movers; for the same things happening, finite things are rather always to be assumed; since in things which subsist naturally, it is necessary, that the finite and that which is better, if possible, sbould rather be inherent. But it is sufficient, though it be one, that the first of things immoveable, being perpetual, should be to other things the principle of motion. From this also it is evident, that the first mover should be a certain one and perpetual; for it has been demonstrated, that it is necessary motion should always exist. And if it always. is, it is also necessary that it should be continued; for that which al ways is, is continued; but that which is successive is not continued. If too, it is continued, it is one; but the motion is one, which is from one mover, and of one thing which is moved: for if another and another thing moves any thing, the whole motion is not continued but successive.
