The Lives and Opinions of Eminent Philosophers

by Diogenes Laertius

“However, one must not believe that every kind of magnitude exists in atoms, lest we find ourselves contradicted by phænomena. But we must admit that there are atoms of different magnitude, because, as that is the case, it is then more easy to explain the impressions and sensations; at all events, I repeat, it is not necessary for the purpose of explaining the differences of the qualities, to attribute to atoms every kind of magnitude.

“We must not suppose either, that an atom can become visible to us; for, first of all, one does not see that that is the case, and besides, one cannot even conceive, how an atom is to become visible; besides, we must not believe, that in a finite body there are particles of every sort, infinite in number; consequently, one must not only reject the doctrine of infinite divisibility in parcels smaller and smaller, lest we should be reducing everything to nothing, and find ourselves forced to admit, that in a mass composed of a crowd of elements, existence can reduce itself to non-existence. But one cannot even suppose that a finite object can be susceptible of transformations ad infinitum, or even of transformation into smaller objects than itself; for when once one has said that there are in an object particles of every kind, infinite in number, there is absolutely no means whatever of imagining that this object can have only a finite magnitude; in fact, it is evident that these particles, infinite in number, have some kind of dimension or other, and whatever this dimension may be in other respects, the objects which are composed of it will have an infinite magnitude; in presenting forms which are determined, and limits which are perceived by the senses, one conceives, easily, without its being necessary to study this last question directly, that this would be the consequence of the contrary supposition, and that consequently, one must come to look at every object as infinite.

“One must also admit, that the most minute particle perceptible to the sense, is neither absolutely like the objects which are susceptible of transformation, nor absolutely different from them. It has some characteristics in common with the object which admit of transformation, but it also differs from them, inasmuch as it does not allow any distinct parts to be discerned in it. When then, in virtue of these common characteristics, and of this resemblance, we wish to form an idea of the smallest particle perceptible by the senses, in taking the objects which change for our terms of comparison, it is necessary that we should seize on some characteristic common to these different objects. In this way, we examine them successively, from the first to the last, not by themselves, nor as composed of parts in juxtaposition, but only in their extent; in other words, we consider the magnitudes by themselves, and in an abstract manner, inasmuch as they measure, the greater a greater extent, and the smaller a smaller extent. This analogy applies to the atom, as far as we consider it as having the smallest dimensions possible. Evidently by its minuteness, it differs from all sensible objects, still this analogy is applicable to it; in a word, we establish by this comparison, that the atom really has some extent, but we exclude all considerable dimensions, for the sake of only investing it with the smallest proportions.[141]

“We must also admit, in taking for our guide, the reasoning which discourses to us things which are invisible to the senses, that the most minute magnitudes, those which are not compound magnitudes, and which from the limit of sensible extent, are the first measure of the other magnitudes which are only called greater or less in their relation to the others. For these relations which they maintain with these particles, which are not subject to transformation, suffice to give them this characteristic of first measure. But they cannot, like atoms, combine themselves, and form compound bodies in virtue of any motion belonging to themselves.

“Moreover, we must not say (while speaking of the infinite), that such or such a point is the highest point of it, or the lowest. For height and lowness must not be predicated of the infinite. We know, in reality, that if, wishing to determine the infinite, we conceive a point above our head, this point, whatever it may be, will never appear to us to have the character in question: otherwise, that which would be situated above the point so conceived as the limit of the infinite, would be at the same moment, and by virtue of its relation to the same point, both high and low; and this is impossible to imagine.

“It follows that thought can only conceive that one single movement of transference, from low to high, ad infinitum; and one single movement from high to low. From low to high, when even the object in motion, going from us to the places situated above our heads, meets ten thousand times with the feet of those who are above us; and from high to low, when in the same way it advances towards the heads of those who are below us. For these two movements, looked at by themselves and in their whole, are conceived as really opposed the one to the other, in their progress towards the infinite.

“Moreover, all the atoms are necessarily animated by the same rapidity, when they move across the vacuum, or when no obstacle thwarts them. For why should heavy atoms have a more rapid movement than those which are small and light, since in no quarter do they encounter any obstacle? Why, on the other hand, should the small atoms have a rapidity superior to that of the large ones, since both the one and the other find everywhere an easy passage, from the very moment that no obstacle intervenes to thwart their movements? Movement from low to high, horizontal movement to and fro, in virtue of the reciprocal percussion of the atoms, movement downwards, in virtue of their weight, will be all equal, for in whatever sense the atom moves, it must have a movement as rapid as the thought, till the moment when it is repelled, in virtue of some external cause, or of its own proper weight, by the shock of some object which resists it.

“Again, even in the compound bodies, one atom does not move more rapidly than another. In fact, if one only looks at the continued movement of an atom which takes place in an indivisible moment of time, the briefest possible, they all have a movement equally rapid. At the same time, an atom has not, in any moment perceptible to the intelligence, a continued movement in the same direction; but rather a series of oscillating movements from which there results, in the last analysis, a continued movement perceptible to the senses. If then, one were to suppose, in virtue of a reasoning on things invisible, that, in the intervals of time accessible to thought, the atoms have a continued movement one would deceive one’s self, for that which is conceived by the thought is true as well as that which is directly perceived.

“Let us now return to the study of the affections, and of the sensations; for this will be the best method of proving that the soul is a bodily substance composed of slight particles, diffused over all the members of the body, and presenting a great analogy to a sort of spirit, having an admixture of heat, resembling at one time one, and at another time the other of those two principles. There exists in it a special part, endowed with an extreme mobility, in consequence of the exceeding slightness of the elements which compose it, and also in reference to its more immediate sympathy with the rest of the body. That it is which the faculties of the soul sufficiently prove, and the passions, and the mobility of its nature, and the thoughts, and, in a word, everything, the privation of which is death. We must admit that it is in the soul most especially that the principle of sensation resides. At the same time, it would not possess this power if it were not enveloped by the rest of the body which communicates it to it, and in its turn receives it from it, but only in a certain measure; for there are certain affections of the soul of which it is not capable.