William of Conches refused, on rational, physical grounds, to believe in the possibility of a chaos preëxisting the Creation.[595] Having accepted the classical doctrine whereby the four elements were arranged in concentric spheres in order from heaviest to lightest,[596] he was unable to conceive of a time when they could have been so intermingled that they contradicted this law, though there may have been a time, he conceded, when the earth was completely enveloped in a thick mantle of water reaching very high and when air and fire themselves were denser than they now are. Such a condition, William thought, was that described in Genesis i, 2.[597] PROCESSES OF THE CREATION _Theodoric of Chartres’ Theory_ (2) How was the universe converted into its present form after God had once created it? Most commentators answered this either by saying or tacitly implying that it was through the immediate operation of God’s will alone. Theodoric of Chartres’ theory, therefore, is peculiarly interesting, because Theodoric maintained that the formation of the universe resulted from what we should now style a series of purely mechanical and chemical reactions which began, once the composition of the _materia_ was completed, on the first day. For its time this was an extremely hazardous view, akin in some respects to the modern belief in the sufficiency of physical and chemical action to produce practically all observable phenomena. Let us examine Theodoric’s theory in a little greater detail. In Genesis i, 2, we read the words, “And the spirit of God moved upon the face of the waters.” Theodoric explained that by the “waters” was meant the whole of matter:[598] the “spirit of God” was that which was destined to give order and form to the chaos, that is to say the “force which fashioned” or “operated” (_virtus artifex_ or _virtus operatrix_). Plato had called this force the World Soul, the Christians called it the Holy Ghost,[599] and through its agency the evolution of the universe out of chaos by physical processes was rendered possible.