The earth's natural place and the philosophers' theories of heaven

And clearly, wherever the parts are carried, the whole will be pushed together toward that same place. If stones and wood and all earthy things are carried downward, then this would also be the proper and fitting position for the whole earth. And if any light thing is carried from the middle, clearly it will move toward the highest point. So the proper movement for the heaviest things is downward, and reason has shown that downward means toward the middle. Do not be surprised, then, that the earth never falls out of place, since it holds the middle as its natural position. For it is absolutely necessary that it remain in place, or else, if it moves contrary to nature, it departs from its proper seat. If any of these arguments seems persuasive to you, transfer your wonder to the wisdom of God who arranged things this way. For amazement at the greatest things is not diminished when the manner in which something marvelous happens is discovered. But if not, then at least let the simplicity of faith be stronger than logical demonstrations.

We might say the same things about heaven as well: the wise men of the world have composed very many-worded treatises about the heavenly nature. Some have said that it is composed of the four elements, since it is tangible and visible, sharing in earth because of its resistance, in fire because it is seen, and in the remaining elements because of the mixture. Others, rejecting this argument as unconvincing, introduced a certain fifth nature of body for the constitution of heaven, improvising it from themselves and by themselves. And among them there is something called the ethereal body, which they say is neither fire nor air nor earth nor water, nor in general any one of the simple bodies. They reason that the simple bodies have movement in a straight line as their proper motion, light things being carried upward and heavy things downward. But upward and downward are not the same as circular whirling, and in general a straight line differs enormously from revolution in a circle. And things whose natural movements are different must necessarily, they say, also have different essences. But neither can we suppose that heaven is composed of the primary bodies, which we call elements, because things composed of different materials cannot have smooth and unforced movement, since each of the simple bodies present in composite things has one impulse or another from nature. Therefore composite things are first of all held together with labor in their continuous movement, because one movement cannot be well-fitted and congenial to all the opposing elements; rather, the movement proper to the light element is hostile to the heaviest. For when we move upward, we are weighed down by the earthy element; and when we are carried downward, we do violence to the fiery element, dragging it down contrary to nature. And this dragging of the elements in opposite directions is an occasion of falling apart. For what is forced and contrary to nature, after resisting for a little while—and that violently and with difficulty—quickly dissolves into the things from which it was composed, as each of the elements that came together returns to its proper place.