It is clear that each of the four elements are opposed to each other in their natures, their positions and their motions, for of all things that move from the centre, fire is swiftest, and likewise, of all the things that move to the centre, earth is swiftest; thus, earth and fire are opposed to each other on account of the heating properties of fire producing lightness in it, and on account of the cold properties of earth producing heaviness in it. Observe, when we say that earth and fire, or two other elements, are opposed to each other, that it is the properties of the elements that are understood then to be opposed to each other and not their substances, for the philosopher says in the Liber Praedicamentorum, Substanti nihil est contrarium, the substance has nothing of contrariety. Thus when we say that fire is hot and dry, and earth cold and dry, the heat and cold of those two elements are opposed to each other; while they are in agreement with each other, inasmuch as the dryness effects speed in them.
Thus air and water agree with each other and are opposed to each other. They agree in the passive properties, i.e., the dampness that is the cause of tardiness in both. They are opposite in the active properties, i.e., the heat which is the cause of lightness in air and coldness which is the cause of heaviness in water. Thus fire and water are opposite to each other in their active and passive qualities, since fire is warm, dry, swift and light, and water is cold, wet, slow and heavy. Finally, it is clear that things which have a direct motion remain in their own natural places, provided they are not forced out of them. When one element is changed into another by the force of the second element, or when one element is displaced by force from its own natural position, as soon as it gets an opportunity or a little help, or when there is no opposition to it, it returns quickly and suddenly to its own nature and its own natural position.
Again, it is clear that everything that moves from the centre is hot and everything that moves to the centre is cold, and that everything that accelerates the motion is unquestionably dry and that everything that retards the motion is unquestionably wet. Thus the Blessed Creator created and arranged the world with its four elements.