Aristotle

"[I]ts gravity is the cause; and that which is heavy abides in the middle, and the earth is in the middle: in like manner also, the infinite will abide in itself, through some other cause... and will itself support itself. ...[T]he places of the whole and the part are of the same species; as of the whole earth and a clod, the place is downward; and of the whole of fire, and a spark, the place is upward. So that if the place of the infinite is in itself, there will be the same place also of a part of the infinite."

"I do believe for certain, that he [Aristotle] first procured, by the help of the senses, such experiments and observations as he could, to assure him as much as was possible of the conclusion, and that he afterwards sought out the means how to demonstrate it; for this is the usual course in demonstrative sciences. And the reason thereof is, because when the conclusion is true, by the help of the resolutive method, one may hit upon some proposition before demonstrated, or come to some principle known per se; but if the conclusion be false, a man may proceed in infinitum, and never meet with any truth already known."

"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."

"[A]ll things as subsist from nature appear to contain in themselves a principle of motion and permanency; some according to place, others according to increase and diminuation; and others according to change in quality."

"According to one mode... nature is thus denominated, viz. the first subject matter to every thing which contains in itself the principle of motion and mutation. But after another mode it is denominated form, which subsists according to definition: for as art is called that which subsists according to art, and that which is artificial; so likewise nature is both called that which is according to nature, and that which is natural. ...that which is composed from these is not nature, but consists from nature; as, for instance, man. And this is nature in a greater degree than matter: for every thing is then said to be, when it is form in energy... entelecheia, rather than when it is incapacity."

"Since... nature is a principle of motion and mutation... it is necessary that we should not be ignorant of what motion is... But motion appears to belong to things continuous; and the infinite first presents itself to the view in that which is continuous. ...[F]requently ...those who define the continuous, employ the nature or the infinite, as if that which is divisible to infinity is continuous."

"There is... something which is in energy only; and there is something which is both in energy and capacity. ...of relatives, one is predicated as according to excess and defect: another according to the effective and passive, and, in short, the motive, and that which may be moved... Motion, however, has not a substance separate from things... But each of the categories subsists in a twofold manner in all things. Thus... one thing pertaining to it is form, and another privation. ...So the species of motion and mutation are as many as those of being. But since in every genus of things, there is that which is in entelecheia, and that which is in capacity; motion is the entelecheia of that which is in capacity... That there is energy, therefore, and that a thing then happens to be moved, when this energy exists, and neither prior nor posterior to it, is manifest. ... [N]either motion nor mutation can be placed in any other genus; nor have those who have advanced a different opinion concerning it spoken rightly. ...for by some motion is said to be difference, inequality, and non-being; though it is not necessary that any of these should be moved... Neither is mutation into these, nor from these, rather than from their opposites. ...The cause, however, why motion appears to be indefinite, is because it can neither be simply referred to the capacity, nor to the energy of beings. ...[I]t is difficult to apprehend what motion is: for it is necessary to refer it either to privation, or to capacity, or to simple energy; but it does not appear that it can be any of these. The above-mentioned mode, therfore remains, viz. that it is a certain energy; but... difficult to be perceived, but which may have a subsistence."

"[I]t is impossible for motion to subsist without place, and void, and time."

"[B]ecause that which is finite is always bounded with reference to something... it is necessary that there should be no end... [N]umber also appears to be infinite, and mathematical magnitudes, and that which is beyond the heavens. And since that which is beyond is infinite, body also appears to be infinite, and it would seem that there are infinite worlds; for why is there rather void here than there? ...If also there is a vacuum, and an infinite place, it is necessary that there should be an infinite body: for in things which have a perpetual subsistence, capacity differs nothing from being. The speculation of the infinite is, however, attended with doubt: for many impossibilities happen both to those who do not admit that it has a subsistence, and to those who do. ...It is ...especially the province of a natural philosopher to consider if there be a sensible infinite magnitude."

"[I]t is impossible that each of the elements should be infinite. For that is body which has interval on all sides; and that is infinite which has extension without bound."

"[H]ow will one part of the infinite be above, and another below? Or how will it have extremes or a middle? Further still, every sensible body is in place; but the species and differences of place are upward and downward, before and behind, to the right hand and to the left: and these things not only thus subsist with relation to us, and by position, but have a definite subsistence in the universe itself. But it is impossible that these things should be in the infinite: and... that there should be an infinite place. But every body is in place; and therefore it is also impossible that there should be an infinite body. ...[T]herefore ...there is not an infinite body in energy."

"[T]he ancient philosophers... all of them assert that the elements, and those things which are called by them principles, are contraries, though they establish them without reason, as if they were compelled to assert this by truth itself. They differ, however... that some of them assume prior, and others posterior principles; and some of them things more known according to reason, but others such as are more known according to sense: for some establish the hot and the cold, others the moist and the dry, others the odd and the even, and others strife and friendship, as the causes of generation. ...in a certain respect they assert the same things, and speak differently from each other. They assert different things... but the same things, so far as they speak analogously. For they assume principles from the same co-ordination; since, of contraries, some contain, and others are contained."