Timaeus

but as regards the thinness of its sides and the acuteness of its angles and the smallness of its particles and the rapidity of its motion—owing to all which properties fire is intense and keen and sharply cuts whatever it encounters,—these properties we must explain by recalling the origin of its form, how that it above all others is the one substance which so divides our bodies and minces them up as to produce naturally both that affection which we call heat and its very name. The opposite affection is evident, but none the less it must not lack description. When liquids with larger particles, which surround the body, enter into it they drive out the smaller particles; but as they cannot pass into their room they compress the moisture within us, so that in place of non-uniformity and motion they produce immobility and density, as a result of the uniformity and compression. But that which is being contracted contrary to nature fights, and, in accordance with its nature, thrusts itself away in the contrary direction. And to this fighting and shaking we give the names of trembling and shivering; while this affection as a whole, as well as the cause thereof, is termed cold. By the term hard we indicate all the things to which our flesh gives way; and by the term soft all those which give way to our flesh; and these terms are similarly used relatively to each other. Now a substance gives way when it has its base small; but when it is constructed of quadrangular bases, being very firmly based, it is a most inelastic form; and so too is everything which is of very dense composition and most rigid. The nature of heavy and light would be shown most clearly if, along with them, we examined also the nature of above and below, as they are called. That there really exist two distinct and totally opposite regions, each of which occupies one-half of the Universe—the one termed below, towards which move all things possessing any bodily mass, and the other above, towards which everything goes against its will,— this is a wholly erroneous supposition For inasmuch as the whole Heaven is spherical, all its outermost parts, being equally distant from the center, must really be outermost in a similar degree; and one must conceive of the center, which is distant from all the outermost parts by the same measures, as being opposite to them all. Seeing, then, that the Cosmos is actually of this nature, which of the bodies mentioned can one set above or below without incurring justly the charge of applying a wholly unsuitable name? For its central region cannot rightly be termed either above or below, but just central; while its circumference neither is central nor has it any one part more divergent than another from the center or any of its opposite parts. But to that which is in all ways uniform, what opposite names can we suppose are rightly applicable, or in what sense?