Besides the radical distinction between Dogmatic and Skeptical Atheism, we must consider the difference between _the four great leading systems_ which have been applied to account for the existing order of Nature, without the recognition of a living, intelligent, personal God. There are many specific varieties of Atheism; but, ultimately, they may be reduced to _four_ classes. The _first_ system assumes and asserts the eternal existence of THE COSMOS; that is, of the present order of Nature, with all its laws and processes, its tribes and races, whether of vegetable or animal life; and affirms that the world, as now constituted, never had a beginning, and that it will never have an end. This has been called the Aristotelian Hypothesis, because Aristotle, while he spoke of a Supreme Mind or Reason, maintained not only the eternity of matter, but also the eternity of "substantial forms and qualities." The _second_ system affirms, not the eternal existence of THE COSMOS,--for the commencement of the existing order of Nature is admitted to be comparatively recent,--but the eternal existence of Matter and Motion; and attempts to account for the origin of the world and of the races by which it is peopled, either by ascribing it, with Epicurus, to a fortuitous concourse of atoms, or, with more modern Speculatists, to a law of progressive development. This has been called the Epicurean Hypothesis, because Epicurus, while nominally admitting the existence of God, denied the creation of the world, and ascribed its origin to atoms supposed to have been endued with motion or certain inherent properties and powers, and to have been self-existent and eternal. The _third_ system affirms the coexistence and coeternity of God and the World; and, while it admits a distinction between the two, represents them as so closely and necessarily conjoined, that God can be regarded only as the Soul of the World,--superior to matter, as soul is to body, but neither anterior to it, nor independent of it, and subject, as matter itself is, to the laws of necessity and fate. This has been called the Stoical System; since the Stoics, notwithstanding all their sublime moral speculations and their frequent recognition of God, taught that God sustains the same relation to the World as the soul of man does to his body.