Epicurus, therefore, not only differed from Aristippus with regard to feelings, by referring all feelings to impressions from without, of which he considered them true representations, but he felt himself called upon to oppose the Cyrenaic contempt for theories of nature, just as the Stoics had opposed the Cynic contempt for science. To the physics of Democritus he looked for a scientific basis for his ethics, just as they had looked to the system of Heraclitus. But the closer he clung to Democritus, owing to the weakness of his own interest in nature, the more it becomes apparent that his whole study of nature was subservient to a moral purpose, and hence of a purely relative value. Accordingly, he had not the least hesitation in setting consistency at defiance, by assuming the swerving aside of atoms and the freedom of the will. It is not only altogether improbable that Epicurus was but a second edition of Democritus—for history knows of no such repetitions—but as a matter of fact it is false. Closer observation proves that even when the two philosophers agree in individual statements, the meaning which they attach to these assertions and the whole spirit of their systems are widely divergent. Democritus aims at explaining natural phenomena by natural causes. He wishes, in short, for a science of nature purely for its own sake. Epicurus wishes for a view of nature which shall be able to avert disturbing influences from man’s inner life. Natural science stands with him entirely in the service of ethics. If in point of substance his system is borrowed from another system, yet its whole position and treatment supposes an entirely new view of things. The Socratic introspection, and the Sophistic resolution of natural philosophy into personal rationalising, are its historical antecedents; and it owes its existence to that general dislike for pure theory, which constitutes the common peculiarity of all the post-Aristotelian systems. [(4) Relation to Aristotle and Plato.] Excepting the systems named, Epicureanism, so far as is known, is connected with no other previous system. Even its attack upon those systems appears to have consisted of general dogmatic and superficial statements. Still it must not be forgotten that Epicureanism presupposes the line of thought originated by Socrates, not only as found in the collateral Cyrenaic branch, but as found in the main line of regular development by Plato and Aristotle. The view of Plato and Aristotle, which distinguishes the immaterial essence from the sensible appearance of things, and attributes reality only to the former, is undoubtedly attacked by Epicurus as by Zeno, on metaphysical grounds. Practically, however, he approaches very much nearer to this view in all those points in which his teaching deviates from the Cyrenaic and resembles that of the Stoics.