Since we have undertaken to make a diligent search into Nature, I cannot but conclude it necessary to declare what Nature is. It is very absurd to attempt a discourse of the essence of natural things, and not to understand what is the power and sphere of Nature. If Aristotle be credited, Nature is the principle of motion and rest, in that thing in which it exists principally and not by accident. For all things that are conspicuous to our eyes, which are neither fortuitous nor necessary, nor have a divine original, nor acknowledge any such like cause, are called natural and enjoy their proper nature. Of this sort are earth, fire, water, air, plants, animals; to these may be added all things produced from them, such as showers, hail, thunders, hurricanes, and winds. All these confess they had a beginning, none of these were from eternity, but had something as the origin of them; and likewise animals and plants have a principle whence they are produced. But Nature, which in all these things hath the priority, is the principle not only of motion but of repose; whatsoever enjoys the principle of motion, the same has a possibility to find a dissolution. Therefore on this account it is that Nature is the principle of motion and rest. CHAPTER II. WHAT IS THE DIFFERENCE BETWEEN A PRINCIPLE AND AN ELEMENT? The followers of Aristotle and Plato conclude that the elements are discriminated from a principle. Thales the Milesian supposeth that a principle and the elements are one and the same thing, but it is evident that they vastly differ one from another. For the elements are things compounded; but we do pronounce that principles admit not of a composition, nor are the effects of any other being. Those which we call elements are earth, water, air, and fire. But we term those principles which have nothing precedent to them out of which they are produced; for otherwise not these themselves, but rather those things whereof they are produced, would be the principles. Now there are some things which have a pre-existence to earth and water, from which they are begotten; to wit, matter, which is without form or shape; then form, which we call ἐντελέχεια (_actuality_); and lastly, privation. Thales therefore is very peccant, by affirming that water is both an element and a principle. CHAPTER III. OF PRINCIPLES, AND WHAT THEY ARE.