manner. perfect sphere, evidently the absolute Eleatic Being subjected to a Heracleitean law of vicissitude and contradiction. For Strife lays hold on the consolidated orb, and by her disintegrating action gradually reduces it to a formless chaos, till, at the close of another world-period, the work of creation begins again. Yet growth and decay are so inextricably intertwined that Empedocles failed to keep up this ideal separation, and was compelled to admit the simultaneous activity of both powers in our everyday experience, so that Nature turns out to be composed of six elements instead of four, the mind which perceives it being constituted in a precisely similar But Love, although on the whole victorious, can only gradually get the better of her retreating enemy, and Nature, as we know it, is the result of their continued conflict. Empedocles described the process of evolution, as he conceived it, in somewhat minute detail. Two points only are of much interest to us, his alleged anticipation of the Darwinian theory and his psychology. The former, such as it was, has occasionally been attributed to Lucretius, but the Roman poet most probably copied Epicurus, although the very brief summary of that philosopher's physical system preserved by Diogenes Laertius contains no allusion to such a topic. We know, however, that in Aristotle's time a theory identical with that of Lucretius was held by those who rejected teleological explanations of the world in general and of living organisms in particular. All sorts of animals were produced by spontaneous generation; only those survived which were accidentally furnished with appliances for procuring nourishment and for propagating their kind. The notion itself originated with Empedocles, whose fanciful suppositions have already been mentioned in a different connexion. Most assuredly he did not offer it as a solution of problems which in his time had not yet been mooted, but as an illustration of the confusion which prevailed when Love had only advanced a little way in her ordering, harmonising, unifying task. Prantl, writing a few years before the appearance of Mr. Darwin's book on the Origin of Species, and therefore without any prejudice on the subject, observes with truth that this theory of Empedocles was deeply rooted in the mythological conceptions of the time. Perhaps he was seeking for a rationalistic explanation of the centaurs, minotaurs, hundred-handed giants, and so forth, in whose existence he had not, like Lucretius, learned completely to disbelieve. His strange supposition was afterwards freed from its worst extravagances; but even as stated in the De Rerum Naturâ, it has no claim whatever to rank as a serious hypothesis. Anything more unlike the Darwinian doctrine, according to which all existing species have been evolved from less highlyorganised ancestors by the gradual accumulation of minute differences, it would be difficult to conceive. Every thinker of antiquity, with one exception, believed in the immutability of natural species. They had existed unchanged from all eternity, or had sprung up by spontaneous generation from the earth's bosom in their present form. The solitary dissentient was Anaximander, who conjectured that man was descended from an aquatic animal.2 Strange to say, this lucky guess has not yet been quoted as an argument against the Ascidian pedigree. It is chiefly the enemies of Darwinism who are eager to find it anticipated in Empedocles or Lucretius. By a curious inversion of traditionalism, it is fancied that a modern discovery can be upset by showing that somebody said something of the kind more than two thousand years ago. Unfortunately authority has not the negative value of disproving the principles which it supports. We must be content to accept the truths brought to light by observation and reasoning, even at the risk of finding ourselves in humiliating agreement with a philosopher of antiquity.3 Prantl, Aristoteles' Physik, p. 484. Passing from life to mind, we find Empedocles teaching an even more pronounced materialism than Parmenides, inasmuch as it is stated in language of superior precision. Our souls are, according to him, made up of elements like those which constitute the external world, each of these being perceived by a corresponding portion of the same substances within ourselves-fire by fire, water by water, and so on with the rest. It is a mistake to suppose that speculation begins from a subjective stand-point, that men start with a clear consciousness of their own personality, and proceed to construct an objective universe after the same pattern. Doubtless they are too prone to personify the blind forces of Nature, and Empedocles himself has just supplied us with an example of this tendency, but they err still more by reading outward experience into their own souls, by materialising the processes of consciousness, and resolving human personality into a loose confederacy of inorganic units. Even Plato, who did more than anyone else towards distinguishing between mind and body, ended by laying down his psychology on the lines of an astronomical system. Meanwhile, to have separated the perception of an object from the object itself, in ever so slight a degree, was an important gain to thought. Epicureanism, has stated that, according to Epicurus, 'the very animals which are found upon the earth have been made what they are by slow processes of selection and adaptation through the experience of life;' and he proceeds to call the theory in question, 'ultra-Darwinian' (Epicureanism, p. 114). Lucretius—the authority quoted-says nothing about 'slow processes of adaptation,' nor yet does he say that the animals were 'made what they are' by 'selection,' but by the procreative power of the earth herself. Picking out a ready-made pair of boots from among a number which do not fit is a very different process from manufacturing the same pair by measure, or wearing it into shape. To call the Empedoclean theory ultra-Darwinian, is like calling the Democritean or Epicurean theory of gravitation ultra-Newtonian. And Mr. Wallace seems to admit as much, when he proceeds to say on the very same page, 'Of course in this there is no implication of the peculiarly Darwinian doctrine of descent or development of kind from kind with structure modified and complicated to meet changing circumstances.' (By the way, this is not a peculiarly Darwinian doctrine, for it originated with Lamarck, spontaneous variation and selection being the additions made by the English naturalists). But what becomes then of the 'slow processes of adaptation' and the 'ultra-Darwinian theory' spoken of just before? We must not omit to notice a hypothesis by which Empedocles sought to elucidate the mechanism of sensation, and which was subsequently adopted by the atomic school; indeed, as will presently be shown, we have reason to believe that the whole atomic theory was developed out of it. He held that emanations were being continually thrown off from the surfaces of bodies, and that they penetrated into the organs of sense through fine passages or pores. This may seem a crude guess, but it is at any rate much more scientific than Aristotle's explanation. According to the latter, possibilities of feeling are converted into actualities by the presence of an object. In other words, we feel when and because we do; a safe assertion, but hardly an addition to our positive knowledge of the subject. We have seen how Greek thought had arrived at a perfectly just conception of the process by which all physical transformations are effected. The whole extended universe is an aggregate of bodies, while each single body is formed by a combination of everlasting elements, and is destroyed by their separation. But if Empedocles was right, if these primary substances were no other than the fire, air, water, and earth of everyday experience, what became of the Heracleitean law, confirmed by common observation, that, so far from remaining unaltered, they were continually passing into one another? To this question the atomic theory gave an answer so conclusive, that, although ignored or contemned by later schools, it was revived with the great revival of science in the sixteenth century, was successfully employed in the explanation of every order of phenomena, and still remains the basis of all physical enquiry. The undulatory theory of light, the law of universal gravitation, and the laws of chemical combination can only be expressed in terms implying the existence of atoms; the laws of gaseous diffusion, and of thermodynamics generally, can only be understood with their help; and the latest develop D ments of chemistry have tended still further to establish their reality, as well as to elucidate their remarkable properties. In the absence of sufficient information, it is difficult to determine by what steps this admirable hypothesis was evolved. Yet, even without external evidence, we may fairly conjecture that, sooner or later, some philosopher, possessed of a high generalising faculty, would infer that if bodies are continually throwing off a flux of infinitesimal particles from their surfaces, they must be similarly subdivided all through; and that if the organs of sense are honeycombed with imperceptible pores, such may also be the universal constitution of matter. Now, according to Aristotle, Leucippus, the founder of atomism, did actually use the second of these arguments, and employed it in particular to prove the existence of indivisible solids. Other considerations equally obvious suggested themselves from another quarter. If all change was expressible in terms of matter and motion, then gradual change implied interstitial motion, which again involved the necessity of fine pores to serve as channels for the incoming and outgoing molecular streams. Nor, as was supposed, could motion of any kind be conceived without a vacuum, the second great postulate of the atomic theory. Here its advocates directly joined issue with Parmenides. The chief of the Eleatic school had, as we have seen, presented being under the form of a homogeneous sphere, absolutely continuous but limited in extent. Space dissociated from matter was to him, as afterwards to Aristotle, non-existent and impossible. It was, he exclaimed, inconceivable, nonsensical. Unhappily inconceivability is about the worst negative criterion of truth ever yet invented. His challenge was now By a curious coincidence, the atomic constitution of matter still finds its strongest proof in optical phenomena. Light is propagated by transverse waves, and such waves are only possible in a discontinuous medium. But if the luminiferous ether is composed of discrete particles, so also must be the matter which it penetrates in all directions. 2 Ar. De Gen. et Corr., I., viii., 325, b, 5. |