Such, in brief, are the main alternatives available for a naturalistic theory of being, in consequence of the historical development of the fundamental conceptions of natural science.
§ 109. We turn now to an examination of the manner in which naturalism, equipped with working principles, seeks to meet the special requirements of philosophy. The conception of the unity of nature is directly in the line of a purely scientific development, but naturalism takes the bold and radical step of regarding nature so unified as coextensive with the real, or at any rate knowable, universe. It will be remembered that among the early Greeks Anaxagoras had referred the creative and formative processes of nature to a non-natural or rational agency, which he called the _Nous_. The adventitious character of this principle, the external and almost purely nominal part which it played in the actual cosmology of Anaxagoras, betrayed it into the hands of the atomists, with their more consistently naturalistic creed. Better, these maintain, the somewhat dogmatic extension of conceptions proved to be successful in the description of nature, than a vague dualism which can serve only to distract the scientific attention and people the world with obscurities. There is a remarkable passage in Lucretius in which atomism is thus written large and inspired with cosmical eloquence:
"For verily not by design did the first-beginnings of things station themselves each in its right place guided by keen intelligence, nor did they bargain sooth to say what motions each should assume, but because many in number and shifting about in many ways throughout the universe, they are driven and tormented by blows during infinite time past, after trying motions and unions of every kind at length they fall into arrangements such as those out of which our sum of things has been formed, and by which too it is preserved through many great years, when once it has been thrown into the appropriate motions, and causes the streams to replenish the greedy sea with copious river waters, and the earth, fostered by the heat of the sun, to renew its produce, and the race of living things to come up and flourish, and the gliding fires of ether to live: all which these several things could in no wise bring to pass, unless a store of matter could rise up from infinite space, out of which store they are wont to make up in due season whatever has been lost."[240:10]