Postponing further reference to this theory until the great name of Lucretius, its Roman exponent, is reached, we find a genuine scientific method making its first start in the person of Aristotle. This remarkable man, the founder of the experimental school, and the Father of Natural History, was born 384 BC at Stagira in Macedonia. In his eighteenth year he left his native place for Athens, where he became a pupil of Plato. Disappointed, as it is thought, at not succeeding his master in the Academy, he removed to Mytilene in the island of Lesbos, where he received an invitation from Philip of Macedon to become tutor to his son, the famous Alexander the Great. When Alexander went on his expedition to Asia, Aristotle returned to Athens, teaching in the “school” which his genius raised to the first rank. There he wrote the greater part of his works, the completion of some of which was stopped by his death at Chalcis in 322. The range of his studies was boundless, but in this brief notice we must limit our survey—and the more so because Aristotle’s speculations outside natural history abound in errors—to his pioneer work in organic evolution. Here, in the one possible method of reaching the truth, theory follows observation. Stagira lay on the Strymonic gulf, and a boyhood spent by the seashore gave Aristotle ample opportunity for noting the variations, and withal gradations, between marine plants and animals, among which last-named it should be noted as proof of his insight that he was keen enough to include sponges. Here was laid the foundation of a classification of life-forms on which all corresponding attempts were based. Then, he saw, as none other before him had seen, and as none after him saw for centuries, the force of heredity, that still unsolved problem of biology. Speaking broadly of his teaching, the details of which would fill pages, its main features are (1) His insistence on observation. In his History of Animals he says “we must not accept a general principle from logic only, but must prove its application to each fact. For it is in facts that we must seek general principles, and these must always accord with facts. Experience furnishes the particular facts from which induction is the pathway to general laws.” (2) His rejection of chance and assertion of law, not, following a common error, of law personified as cause, but as the term by which we express the fact that certain phenomena always occur in a certain order. In his Physics Aristotle says that “Jupiter rains not that corn may be increased, but from necessity. Similarly, if some one’s corn is destroyed by rain, it does not rain for this purpose, but as an accidental circumstance. It does not appear to be from fortune or chance that it frequently rains in winter, but from necessity.” (3) On the question of the origin of life-forms he was nearest of all to its modern solution, setting forth the necessity “that germs should have been first produced, and not immediately animals; and that soft mass which first subsisted was the germ. In plants, also, there is purpose, but it is less distinct; and this shows that plants were produced in the same manner as animals, not by chance, as by the union of olives with grape vines. Similarly, it may be argued, that there should be an accidental generation of the germs of things, but he who asserts this subverts Nature herself, for Nature produces those things which, being continually moved by a certain principle contained in themselves, arrive at a certain end.” In the eagerness of theologians to discover proof of a belief in one God among the old philosophers, the references made by Aristotle to a “perfecting principle,” an “efficient cause,” a “prime mover,” and so forth, have been too readily construed as denoting a monotheistic creed which, reminding us of the “one god” of Xenophanes, is also akin to the Personal God of Christianity. “The Stagirite,” as Mr. Benn remarks (Greek Philosophers, vol. i, p. 312), “agrees with Catholic theism, and he agrees with the First Article of the English Church, though not with the Pentateuch, in saying that God is without parts or passions, but there his agreement ceases. Excluding such a thing as divine interference with all Nature, his theology, of course, excludes the possibility of revelation, inspiration, miracles, and grace.” He is a being who does not interest himself in human affairs.
But, differ as the commentators may as to Aristotle’s meaning, his assumed place in the orthodox line led, as will be seen hereafter, to the acceptance of his philosophy by Augustine, Bishop of Hippo, in the fourth century, and by other Fathers of the Church, so that the mediæval theories of the Bible, blended with Aristotle, represent the sum of knowledge held as sufficient until the discoveries of Copernicus in the sixteenth century upset the Ptolemaic theory with its fixed earth and system of cycles and epicycles in which the heavenly bodies moved. He thereby upset very much besides. Like Anaximander and others, Aristotle believed in spontaneous generation, although only in the case of certain animals, as of eels from the mud of ponds, and of insects from putrid matter. However, in this, both Augustine and Thomas Aquinas, and many men of science down to the latter part of the seventeenth century, followed him. For example, Van Helmont, an experimental chemist of that period, gave a recipe for making fleas; and another scholar showed himself on a level with the unlettered rustics of to-day, who believe that eels are produced from horse hairs thrown into a pond.
Of deeper interest, as marking Aristotle’s prevision, is his anticipation of what is known as Epigenesis, or the theory of the development of the germ into the adult form among the higher individuals through the union of the fertilizing powers of the male and female organs. This theory, which was proved by the researches of Harvey, the discoverer of the circulation of the blood, and is accepted by all biologists to-day, was opposed by Malpighi, an Italian physician, born in 1628, the year in which Harvey published his great discovery, and by other prominent men of science down to the last century. Malpighi and his school contended that the perfect animal is already “preformed” in the germ; for example, the hen’s egg, before fecundation, containing an excessively minute, but complete, chick. It therefore followed that in any germ the germs of all subsequent offspring must be contained, and in the application of this “box-within-box” theory its defenders even computed the number of human germs concentrated in the ovary of mother Eve, estimating these at two hundred thousand millions!
When the “preformation” theory was revived by Bonnet and others in the eighteenth century, Erasmus Darwin, grandfather of Charles Darwin, passed the following shrewd criticism on it: “Many ingenious philosophers have found so great difficulty in conceiving the manner of reproduction in animals that they have supposed all the numerous progeny to have existed in miniature in the animal originally created. This idea, besides its being unsupported by any analogy we are acquainted with, ascribes a greater continuity to organized matter than we can readily admit. These embryons … must possess a greater degree of minuteness than that which was ascribed to the devils who tempted St. Anthony, of whom twenty thousand were said to have been able to dance a saraband on the point of a needle without the least incommoding each other.”
Although no theistic element could be extracted by the theologians of the early Christian Church from the systems of Empedocles and Democritus, thereby securing them a share in the influence exercised by the great Stagirite, they were formative powers in Greek philosophy, and, moreover, have “come by their own” in these latter days. Their chief representative in what is known as the Post-Aristotelian period is Epicurus, who was born at Samos, 342 BC As with Zeno, the founder of the Stoic school, his teaching has been perverted, so that his name has become loosely identified with indulgence in gross and sensual living. He saw in pleasure the highest happiness, and therefore advocated the pursuit of pleasure to attain happiness, but he did not thereby mean the pursuit of the unworthy. Rather did he counsel the following after pure, high, and noble aims, whereby alone a man could have peace of mind. It is not hard to see that in the minds of men of low ideals the tendency towards passivity which lurked in such teaching would aid their sliding into the pursuit of mere animal enjoyment; hence the gross and limited association of the term Epicurean. Epicurus accepted the theory of Leucippus, and applied it all round. The fainéant gods, who dwell serenely