DIADUMENUS. Moreover, calling these four bodies, earth, water, air, and fire, the first elements, they do (I know not how) make some of them simple and pure, and others compound and mixed. For they hold that earth and water keep together neither themselves nor other things, but preserve their unity by the participation of air and force of fire; but that air and fire do both fortify themselves by their own strength, or being mixed with the other two, give them force, permanence, and subsistence. How then is either earth or water an element, if neither of them is either simple, or first, or self-sufficient, but if each wants somewhat from without to contain and keep it in its being? For they have not left so much as a thought of their substance; but this discourse concerning the earth has much confusion and uncertainty, when they say that it subsists of itself; for if the earth is of itself, how has it need of the air to fix and contain it? But neither the earth nor water can any more be said to be of itself; but the air, drawing together and thickening the matter, has made the earth, and again dissolving and mollifying it, has produced the water. Neither of these then is an element, since something else has contributed being and generation to them both.