All this, however, has been put in a way that is more plausible than true. Look at it in this way, my dear Demetrius, said I; when he says of the bodies that some have a motion towards the centre and downwards, others away from the centre and upwards, and others around the centre and in a circular path, in what relation does he take the centre? Cf. Moralia , 925 b and 1054 b. Certainly not in relation to the void, for according to him it does not exist. And according to those for whom it does exist, it has no centre, just as it has no point where it begins or where it ends; for these are limitations, and the infinite has no limitations. And if a man could force himself, by reasoning, to dare the concept of a violent motion of the infinite, what difference, if referred to this, is created for the bodies in their movements? For in the void there is no power in the bodies, nor do the bodies have a predisposition and an impetus, by virtue of which they cling to the centre and have a universal tendency in this one direction. It is equally difficult, in the case of inanimate bodies and an incorporeal and undifferentiated position, to conceive of a movement created from the bodies or an attraction created by the position. Thus one conclusion is left: when the centre is spoken of it is not with reference to any place, but with reference to the bodies. For in this world of ours, which has a single unity in its organization from numerous dissimilar elements, these differences necessarily create various movements towards various objects. Evidence of this is found in the fact that everything, when it undergoes transformation, changes its position coincidently with the change in its substance. For example, dispersion distributes upwards and round about the matter rising from the centre and condensation and consolidation press it down towards the centre and drive it together. On this topic it is not necessary to use more words at present. The truth is that whatever cause one may postulate as the author of these occurrences and changes, that cause will keep each of the worlds together within itself; for each world has earth and sea, and each has its owTn centre and occurrences that affect its component bodies; it has its own transmutations and a nature and a power which preserves each one and keeps it in place. In what lies beyond, whether it be nothing or an infinite void, no centre exists, as has been said; and if there are several worlds, in each one is a centre which belongs to it alone, with the result that the movements of its bodies are its own, some towards it, some away from it, and some around it, quite in keeping with the distinctions which these men themselves make. But anyone who insists that, while there are many centres, the heavy substances are impelled from all sides towards one only, Cf. Moralia , 928 a-b. does not differ at all from him who insists that, while there are many men, the blood from all shall flow together into a single vein and the brains of all shall be enveloped in a single membrane, deeming it a dreadful thing in the case of natural bodies if all the solids shall not occupy one place only and the fluids also only one place. Such a man as that will be abnormal, and so will he be who is indignant if everything constituting a whole has its own parts, of which it makes use in their natural arrangement and position in every case. For that would be preposterous, and so too if anybody called that a world which had a moon somewhere inside it Instead of revolving around it. ; as well call that a man who carries his brains in his heels or his heart in his head! Cf. Demosthenes, Oration vii. 45. But to make more worlds than one, each separate from the other, and to delimit and distinguish the parts belonging to each to go with the whole is not preposterous. For the land and the sea and the heavens in each will be placed to accord with nature, as is fitting; and each of the worlds has its above and below and its round about and its centre, not with reference to another world or the outside, but in itself and with reference to itself.