in theory a race between the hedgehog and the hare.94 The true significance of the destructive criticism brought to bear by Zeno and Melissus on the concepts of unity, plurality, continuity, extension, time, and motion is simply this: that when by a shift of the attention a predicate becomes subject or meaning fossilizes as existence, the terms of the logical process lose their functional reference and grow to be unmeaning and self-contradictory.
We have already remarked that Empedocles, Anaxagoras, and the Atomists sought to solve the problem of the One and the Many, of the subject and the predicate, by shattering the unitary predicate and thus leaving the field to plurality in both spheres. But obviously they were merely postponing the real question. Thought, as well as action, demands a unity somewhere. Hence the absorbing task of these philosophers is to disclose or contrive such a bond of unity. The form which their quest assumed was the search for a basis for physical interaction.95
Empedocles clearly believed that he was solving the difficulty in one form when he instituted the rhythmic libration between unity under the sway of Love and multiplicity under the domination of Hate. But even he was not satisfied with that. While Love brought all the elements together into a sphere and thus produced a unity, it was a unity constituted of a mixture of elements possessing inalienable characters not only different but actually antagonistic. On the other hand, Hate did indeed separate the confused particles, but it effected a sort of unity in that, by segregating the particles of the several elements from the others, it brought like and like together. In so far Aristotle was clearly right in attributing to Love the power to separate as well as to unite. Moreover, it would seem that there never was a moment in which both agencies were not conceived to be operative, to however small an extent.
Empedocles asserted, however, that a world could arise only in the intervals between the extremes of victory in the contest between Love and Hate, when, so to speak, the battle was drawn and there was a general mêlée of the combatants. It may be questioned, perhaps, whether he distinctly stated that in our world everything possessed its portion of each of the elements; but so indispensable did he consider this mixture that its function of providing a physical unity is unmistakable. A further evidence of his insistent demand for unity—the copula—is found in his doctrine that only like can act on like; and the scheme of pores and effluvia which he contrived bears eloquent testimony to the earnest consideration he gave to this matter. For he conceived that all interaction took place by means of them.
Empedocles, then, may be said to have annulled the decree of divorce he had issued for the elements at the beginning. But the solution here too is found, not in the theoretical, but in the practical, sphere; for he never retracts his assertion that the elements are distinct and antagonistic. But even so his problem is defined rather than solved; for after the elements have been brought within microscopic distance of each other in the mixture, since like can act only on like, the narrow space that separates them is still an impassable gulf.96
Anaxagoras endowed his infinitely numerous substances with the same characters of fixity and contrariety that mark the four elements of Empedocles. For him, therefore, the difficulty of securing unity and co-operation in an effective copula is, if that be possible, further aggravated. His grasp of the problem, if we may judge from the relatively small body of documentary evidence, was not so sure as that of Empedocles, though he employed in general the same means for its solution. He too postulates a mixture of all substances, more consciously and definitely indeed than his predecessor. Believing that only like can act on like,97 he is led to assume not only an infinite multiplicity of substances, but also their complete mixture, so that everything, however small, contains a portion of every other. Food, for example, however seeming-simple, nourishes the most diverse tissues of the body. Thus we discover in the universal mixture of substances the basis for co-operation and interaction.
Anaxagoras, therefore, like Empedocles, feels the need of bridging the chasm which he has assumed to exist between his distinct substances. Their failure is alike great, and is due to the presuppositions they inherited from the Eleatic conception of a severe homogeneity which implies an absolute difference from everything else. The embarrassment of Anaxagoras increases with the introduction of the Νοῦς. This agency was conceived with a view to explaining the formation of the world; that is, with a view to mediating between the myriad substances in their essential aloofness and effecting the harmonious concord of concrete things. While, even on the basis of a universal mixture, the function of the Νοῦς was foredoomed to failure, its task was made more difficult still by the definition given to its nature. According to Anaxagoras it was the sole exception to the composite character of things; it is absolutely pure and simple in nature.98 By its definition, then, it is prevented from accomplishing the work it was contrived to do; and hence we cannot be surprised at the lamentations raised by Plato and Aristotle about the failure of Anaxagoras to employ the agency he had introduced. To be sure, the Νοῦς is no more a deus ex machina than were the ideas of Plato or the God of Aristotle. They all labored under the same restrictions.
The Atomists followed with the same recognition of the Many, in the infinitely various kinds of atoms; but it was tempered by the assumption of an essential homogeneity. One atom is distinguished from another by characteristics due to its spatial relations. Mass and weight are proportional to size. Aristotle reports that, though things and atoms have differences, it is not in virtue of their differences, but in virtue of their essential identity, that they interact.99 There is thus introduced a distinction which runs nearly, but not quite, parallel to that between primary and secondary qualities.100 Primary qualities are those of size, shape, and perhaps101 position; all others are secondary. On the other hand, that which is common to all atoms is their corporeity, which does indeed define itself with reference to the primary (spatial) qualities, but not alike in all. The atoms of which the world is constituted are alike in essential nature, but they differ most widely in position.
It is the void that breaks up the unity of the world—atomizes it, if we may use the expression. It is the basis of all discontinuity. Atoms and void are thus polar extremes reciprocally exclusive. The atoms in their utter isolation in space are incapable of producing a world. In order to bridge the chasm between atom and atom, recourse is had to motion eternal, omnipresent, and necessary. This it is that annihilates distances. In the course of their motion atoms collide, and in their impact one upon the other the Atomists find the precise mode of co-operation by which the world is formed.102 To this agency are due what Lucretius happily called "generating motions."
The problem, however, so insistently pursued the philosophers of this time that the Atomists did not content themselves with this solution, satisfactory as modern science has pretended to consider it. They followed the lead of Empedocles and Anaxagoras in postulating a widespread, if not absolutely universal, mixture. Having on principle excluded "essential" differences among the atoms, the impossibility of finally distinguishing essential and non-essential had its revenge. Important as the device of mixture was to Empedocles and Anaxagoras, just so unmeaning ought it to have been in the Atomic philosophy, provided that the hypothesis could accomplish what was claimed for it. It is not necessary to reassert that the assumption of "individua," utterly alienated one from the other by a void, rendered the problem of the copula insoluble for the Atomists.
Diogenes of Apollonia is commonly treated contemptuously as a mere reactionary who harked back to Anaximenes and had no significance of his own. The best that can be said of such an attitude is that it regards philosophical theories as accidental utterances of individuals, naturally well or ill endowed, who happen to express conclusions with which men in after times agree or disagree. A philosophical tenet is an atom, set somewhere in a vacuum, utterly out of relation to everything else. But it is impossible to see how, on this theory, any system of thought should possess any significance for anybody, or how there should be any progress even, or retardation.
Viewed entirely from without, the doctrine of Diogenes would seem to be substantially a recrudescence of that of Anaximenes. Air is once more the element or ἀρχή out of which all proceeds and into which all returns. Again the process of transformation is seen in rarefaction and condensation; and the
