COMMENTS ON STURM
Translation © George MacDonald Ross, 1974–1999
On Nature itself, or the intrinsic force and actions of creatures, in confirmation and illustration of the author’s dynamics
[512] . . . (13) In my opinion, Professor Sturm’s second argument, which is from the nature of motion, is no more conclusive. He says that motion is merely the successive existence of a moving thing in different places. Let us accept this for the moment, even though it is not entirely satisfactory, since it expresses [513] the result of motion rather than its ratio formalis [n.1] (as they call it). But this is not enough to rule out a motive force. For at any given moment of its motion, a body does not merely occupy a space equal to its own dimensions, but also has a conatus or nisus [n.2] towards changing its place, so that its subsequent state follows from its present one by an intrinsic natural force; otherwise at any given moment (and hence at any moment whatever), a moving body A would differ in no respect from a stationary body B, [n.3] and it would follow from Professor Sturm’s opinion, if it were opposed to ours on that point, that there would be absolutely no distinction between bodies, since in a plenum consisting of an intrinsically uniform mass, any distinction within it can only be based on motion; but the ultimate consequence of this would be that there would in fact be no variety in bodies at all, and everything would always have the same characteristics. For if there is no difference between any portion of matter and another one of the same size and shape (which Professor Sturm must admit, having abolished active forces or impetus, and all other qualities and modifications apart from existence in a particular place, becoming different existences at successive instants); and further, if the state [of the universe] at one instant differs from its state at another instant only in virtue of the translation [from one place to another] of portions of matter which have the same size and shape and correspond in every respect, it obviously follows that the states of the corporeal world at different moments can in no way be distinguished, since indistinguishable things are perpetually being substituted for each other. For one part of matter would be distinguished from another only by an extrinsic denomination, that is, in the future, namely because it was going to be in some other place later. But at present there is no distinction, and in fact there would be no basis for a distinction even in the future. For not even in the future would one ever arrive at some true present distinction, since there would be no mark by which one place could be distinguished from another place, or one portion of matter from another portion of matter in the same place (on this hypothesis that matter itself is perfectly uniform). It would even be fruitless to have recourse to shape in addition to motion. For motion is itself the only thing that can give rise to shape (i.e. the marking off and differentiation of distinct parts) in a perfectly similar and undifferentiated mass without any void in it. But if, then, motion contains no distinguishing mark, it will not bestow any on shape either; and since everything taking the place of something previous would be absolutely equivalent to it, no observer, not even an omniscient one, will be able to perceive even the slightest indication of change. Hence everything will be exactly as if no change or differentiation had occurred among bodies, and on this basis it will never be possible to account for the diversity of the appearances we perceive. A precisely analogous situation is the following: imagine two concentric perfect spheres which are absolutely similar to each other and homogeneous, [514] and of which one is enclosed inside the other without the slightest gap between them. Now, whether we suppose the inner one to be revolving or stationary, not even an angel, let alone any other being, could detect any difference between states [of the system] at different times, or have any criterion for determining whether the enclosed sphere were at rest or revolving, and what law of motion it obeyed. In fact it would not even be possible to define where one sphere ended and the other began, because of there being neither a gap nor any difference between them; just as in this case the absence of any difference is by itself enough to make it impossible to tell if one of them is moving [i.e. if they are similar but there is a gap between them, they can be distinguished, but it is still impossible to tell if one is moving]. So it must be regarded as certain (even if those who have not penetrated deeply enough into these matters have been too little aware of the fact) that such cases are foreign to the nature and order of the universe, and that there is no perfect similarity anywhere (which is one of my principal new axioms). It is also a consequence of this that there are not to be found in nature any absolutely hard corpuscles, or a perfectly tenuous fluid (subtle matter diffused everywhere), or those ultimate elements which some [i.e. the Cartesians] have believed in and called [matter] of the first or second [element]. I suspect that Aristotle realised much of this (and in my opinion he was profounder than many people think), and that this is why he thought there must be qualitative change as well as change of place, and that matter is not similar to itself everywhere, otherwise it would not be capable of qualitative change. But this differentiation or diversity of qualities, and hence qualitative change, of which Aristotle did not give a satisfactory account, comes from the various degrees and directions of nisus, and hence from the modifications of the inherent monads. So I think it is obvious from this that bodies must necessarily include something more than uniform mass and its translation [from one place to another], which would bring about no change at all in anything. Certainly, those who postulate atoms and the void do at least give considerable diversification to matter, in that they make it divisible in one place, indivisible in another, and dense in one place, void in another. But it was a long time ago that I realised (abandoning youthful prejudice) that atoms must be rejected altogether with the void. Professor Sturm adds that the continued existence of matter at different times is to be attributed to the divine will; so why (he says) should we not attribute to the divine will the fact that matter exists here and now? I reply that this is undoubtedly due to God, just as everything else is due to God insofar as it involves some perfection. However, just as that first and universal cause does not, in conserving everything, destroy, but rather brings about the natural self-sufficiency of a thing which comes into existence, i.e. its perseverance in existence granted to it once for all; so this same cause will not destroy, but will rather confirm the natural efficacy of a thing stimulated to motion, i.e. its perseverance in acting impressed on it once for all. . . .
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