According to the Stoic philosophy, the criterion for conduct was to live "according to nature." "What is meant by 'rationally'?" asks Epictetus, and answers, "Conformably to nature." "Convince me that you acted naturally, and I will convince you that everything which takes place according to nature takes place rightly." [Footnote: Book III, chap, I; book I, chap. XI.] And Marcus Aurelius writes, "Do not think any word or action beneath you which is in accordance with nature; and never be misled by the apprehension of censure or reproach. I will march on in the path of nature till my legs sink under me. Philosophy will put you upon nothing but what your nature wishes and calls for." [Footnote: Book V.] Of this preaching Bishop Butler says that it is "a manner of speaking, not loose and indeterminate, but clear and distinct, strictly just and true." [Footnote: Preface to Sermons.] In modern times this doctrine has taken the form of exhortation to take our place in the evolutionary process. It is thought by some that to grasp the trend of existing natural forces is to know the direction of duty. We have only to keep in the current, to espouse heartily the "struggle for existence" and rejoice in the "survival of the fittest," because it is nature's way. In a recent book by a Harvard professor we read, "Whatever the order of the universe is, that is the moral order...The laws of natural selection are merely God's regular methods of expressing his choice and approval. The naturally selected are the chosen of God...The whole life of [moral] people will consist in an intelligent effort to adjust themselves to the will thus expressed." [Footnote: T. N. Carver, The Religion Worth Having, pp. 84-89.] It is easy enough to point out, however, that nature man to follow. "In sober truth, nearly all the things which men are hanged or imprisoned for doing to one another, are nature's everyday performances. Nature impales men, breaks them as if on the wheel, casts them to be devoured by wild beasts, crushes them with stones like the first Christian martyr, starves them with hunger, freezes them with cold, poisons them by the quick or slow venom of her exhalations." [Footnote: J. S. Mill, Three Essays on Religion: "Nature," p. 28.] The evolutionary process is cruel and merciless; multitudes perish for every one that survives, and the survivor is not the most deserving, but the strongest or swiftest or cleverest. Why should we imitate such ruthless ways? Nature is to be not followed but improved upon. Not only morality, but most of man's activity, consists in making nature over to suit his needs. "If nature and man are both the works of a Being of perfect goodness, that Being intended nature as a scheme to be amended, not imitated, by man." [Footnote: Ibid, p. 41.]