And this happens in every continuum: as between lines a, b, of which a is greater, there can exist an infinity of intermediate lines, smaller than a, but greater than b (since indeed the excess by which a surpasses b is a line, it will be infinitely divisible): on must however not say that line a infinitely exceeds line b, in such a way , even if b were infinitely augmented, that in the end it would not make up a greater line than a. And thus, by similar reasoning, if we understand that a is the swiftness in a void, but b the swiftness in air, assuredly between a and b there will be able to exist an infinity of swiftnesses, greater than b and smaller than a: one must however not conclude that a exceeds infinitely this b, in such a way that the time during which swiftness a takes place, having been augmented by itself as many times as one wants, can still never exceed the time of swiftness b, and, consequently, that the swiftness of time a is instantaneous. It is therefore evident how this must be understood: The lightness of a void exceeds infinitely the lightness of a medium, hence the swiftness in a void will infinitely exceed the swiftness in a plenum. All that is conceded. That, therefore, the swiftness in the void will be in an instant, is denied.For it can exist in time, but assuredly one briefer than the time of swiftness in a plenum; so that between the time in the plenum and the time in the void there can stand an infinity of times, greater than the latter, but smaller than the former: and thus it is not necessary that motion in the void takes place in an instant, but in a time smaller than is the time of motion in any plenum whatsoever.
Thus, to put it briefly, my whole intent is the following: if there is a heavy thing a, whose proper and natural heaviness is 1000, in any plenum whatever its heaviness will be less than a thousand, and, consequently, the swiftness of its motion in any plenum whatever will be less than a thousand. And if we take a medium, such that the heaviness of a size of it equal to the size of a is only 1, the heaviness of a in this medium will be 999; thus its swiftness also will be 999: and the swiftness of this same a will only be a thousand in the medium where its heaviness is one thousand; and that will be nowhere but in the void.
This is the solution of Aristotle's argument: from this it can be understood quite readily, how in the void it is in no way required that motion be instantaneous. The other arguments of Aristotle are of no soundness and have no necessity. Now to say {1}, for example, that in the void a mobile will no more be moved towards here than towards there, or upward than downward, because the void does not give way more upward or downward but equally on all sides, is childish