According to Empedocles, the four primal elements, earth, air, fire and water, are worked upon by the forces of love and discord. By means of these forces, out of the primal elements are evolved various and horrible monstrosities before the final form of perfection is reached. It is true he did not correctly imagine the stages in the processes of evolution, for instead of a gradual development of one form from another, he describes the process as a haphazard and chaotic one. "Many heads sprouted up without necks, and naked arms went wandering forlorn of shoulders, and solitary eyes were straying destitute of foreheads." These detached portions of bodies coming together by haphazard produced the earlier monstrous forms. "Many came forth with double faces and two breasts, some shaped like oxen with a human front, others, again, of human race with a bull's head." However, the latter part of the evolutionary process as described by Empedocles, when Love takes command, seems especially pertinent as a possible source of Browning's thought: "When strife has reached the very bottom of the seething mass, and love assumes her station in the center of the ball, then everything begins to come together, and to form one whole--not instantaneously, but different substances come forth, according to a steady process of development. Now, when these elements are mingling, countless kinds of things issue from their union. Much, however, remains unmixed, in opposition to the mingling elements, and these, malignant strife still holds within his grasp. For he has not yet withdrawn himself altogether to the extremities of the globe; but part of his limbs still remain within its bounds, and part have passed beyond. As strife, however, step by step retreats, mild and innocent love pursues him with her force divine; things which had been immortal instantly assume mortality; the simple elements become confused by interchange of influences. When these are mingled, then the countless kinds of mortal beings issue forth, furnished with every sort of form--a sight of wonder." Though evolution was no new idea, it had been only a hypothesis arrived at intuitionally or suggested by crude observations of nature until by perfected methods of historical study and of scientific experimentation proof was furnished of its truth as a scientific verity.