Plato and the Other Companions of Sokrates, 3rd ed. Volume 1

Besides these doctrines respecting the great cosmical bodies, Anaxagoras gave explanations of many among the striking phenomena in geology and meteorology — the sea, rivers, earthquakes, hurricanes, hail, snow, &c.174 He treated also of animals and plants — their primary origin, and the manner of their propagation.175 He thought that animals were originally produced by the hot and moist earth; but that being once produced, the breeds were continued by propagation. The seeds of plants he supposed to have been originally contained in the air, from whence they fell down to the warm and moist earth, where they took root and sprung up.176 He believed that all plants, as well as all animals, had a certain measure of intelligence and sentiment, differing not in kind but only in degree from the intelligence and sentiment of men; whose superiority of intelligence was determined, to a great extent, by their possession of hands.177 He explained sensation by the action of unlike upon unlike (contrary to Empedokles, who referred it to the action of like upon like),178 applying this doctrine to the explanation of the five senses separately. But he pronounced the senses to be sadly obscure and insufficient as means of knowledge. Apparently, however, he did not discard their testimony, nor assume any other means of knowledge independent of it, but supposed a concomitant and controlling effect of intelligence as indispensable to compare and judge between the facts of sense when they appeared contradictory.179 On this point, however, it is difficult to make out his opinions.

Anaxagoras, residing at Athens and intimately connected with Perikles, incurred not only unpopularity, but even legal prosecution, by the tenor of his philosophical opinions, especially those on astronomy. To Greeks who believed in Helios and Selênê as not merely living beings but Deities, his declaration that the Sun was a luminous and fiery stone, and the Moon an earthy mass, appeared alike absurd and impious. Such was the judgment of Sokrates, Plato, and Xenophon, as well as of Aristophanes and the general Athenian public.180 Anaxagoras was threatened with indictment for blasphemy, so that Perikles was compelled to send him away from Athens.

That physical enquiries into the nature of things, and attempts to substitute scientific theories in place of the personal agency of the Gods, were repugnant to the religious feelings of the Greeks, has been already remarked.181 Yet most of the other contemporary philosophers must have been open to this reproach, not less than Anaxagoras; and we learn that the Apolloniate Diogenes left Athens from the same cause. If others escaped the like prosecution which fell upon Anaxagoras, we may probably ascribe this fact to the state of political party at Athens, and to the intimacy of the latter with Perikles. The numerous political enemies of that great man might fairly hope to discredit him in the public mind — at the very least to vex and embarrass him — by procuring the trial and condemnation of Anaxagoras. Against other philosophers, even when propounding doctrines not less obnoxious respecting the celestial bodies, there was not the same collateral motive to stimulate the aggressive hostility of individuals.

Contemporary with Anaxagoras — yet somewhat younger, as far as we can judge, upon doubtful evidence — lived the philosopher Diogenes, a native of Apollonia in Krete. Of his life we know nothing except that he taught during some time at Athens, which city he was forced to quit on the same ground as Anaxagoras. Accusations of impiety were either brought or threatened against him:182 physical philosophy being offensive generally to the received religious sentiment, which was specially awakened and appealed to by the political opponents of Perikles.

Diogenes the Apolloniate, the latest in the series of Ionic philosophers or physiologists, adopted, with modifications and enlargements, the fundamental tenet of Anaximenes. There was but one primordial element — and that element was air. He laid it down as indisputable that all the different objects in this Kosmos must be at the bottom one and the same thing: unless this were the fact, they would not act upon each other, nor mix together, nor do good and harm to each other, as we see that they do. Plants would not grow out of the earth, nor would animals live and grow by nutrition, unless there existed as a basis this universal sameness of nature. No one thing therefore has a peculiar nature of its own: there is in all the same nature, but very changeable and diversified.183

Now the fundamental substance, common to all, was air. Air was infinite, eternal, powerful; it was, besides, full of intelligence and knowledge. This latter property Diogenes proved by the succession of climatic and atmospheric phenomena of winter and summer, night and day, rain, wind, and fine weather. All these successions were disposed in the best possible manner by the air: which could not have laid out things in such regular order and measure, unless it had been endowed with intelligence. Moreover, air was the source of life, soul, and intelligence, to men and animals: who inhaled all these by respiration, and lost all of them as soon as they ceased to respire.184

Air, life-giving and intelligent, existed everywhere, formed the essence of everything, comprehended and governed everything. Nothing in nature could be without it: yet at the same time all things in nature partook of it in a different manner.185 For it was distinguished by great diversity of properties and by many gradations of intelligence. It was hotter or colder — moister or drier — denser or rarer — more or less active and movable — exhibiting differences of colour and taste. All these diversities were found in objects, though all at the bottom were air. Reason and intelligence resided in the warm air. So also to all animals as well as to men, the common source of vitality, whereby they lived, saw, heard, and understood, was air; hotter than the atmosphere generally, though much colder than that near the sun.186 Nevertheless, in spite of this common characteristic, the air was in other respects so indefinitely modifiable, that animals were of all degrees of diversity, in form, habits, and intelligence. Men were doubtless more alike among themselves: yet no two of them could be found exactly alike, furnished with the same dose of aerial heat or vitality. All other things, animate and inanimate, were generated and perished, beginning from air and ending in air: which alone continued immortal and indestructible.187