The Summary of Physics Restored

118Those who have taught that earth, water, air, and fire are the world’s elements, distinct in their respective spheres, and that they change into one another by mutual interchange, have investigated Nature’s secrets badly. It will be safer to call them integral parts of the world, or workshops of the elements. For the world’s elements do not display themselves to the senses separated into their own regions; they lie concealed in their matrices until they come together in the generation of mixed bodies and constitute a body. Those parts of the world cannot change into one another, because they differ too greatly. Nor can the single common quality by which those natures are bound together accomplish so great a change that heterogeneous substances become homogeneous—indeed, become entirely the same.