The physical theories of Democritus were and are profoundly interesting as an attempt to answer some of the great questions of natural science—how to account for growth and change, for the fact that earth turns into corn, corn into men, and men again into earth. The early Ionic philosophers had seen that some necessary common basis must be found, and had sought it in water or fire or some other supposed element. The inadequacy of these explanations soon became evident to the rapidly growing Greek intellect, and Democritus found the common basis in atoms, indestructible and indivisible; an infinite number of these were moving through space, differing in shape and hardness; the movement of the atoms had a certain swerve which enabled them to meet, and the meeting of infinite numbers enabled those of the right shape and texture to join and form the things we see (res in Lucretius). Atoms and void—there was nothing else, and nothing else was needed to produce the world we know. This is a purely physical theory and might be held by Napoleon, Cleopatra, or Charles Peace, nor is it capable of being made the subject of a great poem