Pantheism teaches that God and the world are one. The idea of God is identical with that of nature or substance. This pantheistic view is sharply opposed in principle to all the systems we have described, and to all possible forms of theism although there have been many attempts made from both sides to bridge over the deep chasm that separates the two. There is always this fundamental contradiction between them, that in theism God is opposed to nature as an _extramundane_ being, as creating and sustaining the world, and acting upon it from without, while in pantheism God, as an _intramundane_ being, is everywhere identical with nature itself, and is operative _within_ the world as "force" or "energy." The latter view alone is compatible with our supreme law--the law of substance. It follows necessarily that pantheism is _the world-system of the modern scientist_. There are, it is true, still a few men of science who contest this, and think it possible to reconcile the old theistic theory of human nature with the pantheistic truth of the law of substance. All these efforts rest on confusion or sophistry--when they are honest. As pantheism is a result of an advanced conception of nature in the civilized mind, it is naturally much younger than theism, the crudest forms of which are found in great variety in the uncivilized races of ten thousand years ago. We do, indeed, find the germs of pantheism in different religions at the very dawn of philosophy in the earliest civilized peoples (in India, Egypt, China, and Japan), several thousand years before the time of Christ; still, we do not meet a definite philosophical expression of it until the hylozoism of the Ionic philosophers, in the first half of the sixth century before Christ. All the great thinkers of this flourishing period of Hellenic thought are surpassed by the famous Anaximander, of Miletus, who conceived the essential unity of the infinite universe (_apeiron_) more profoundly and more clearly than his master, Thales, or his pupil, Anaximenes. Not only the great thought of the original unity of the cosmos and the development of all phenomena out of the all-pervading primitive matter found expression in Anaximander, but he even enunciated the bold idea of countless worlds in a periodic alternation of birth and death.