Pa. And can inanimate things move of themselves?
Lu. No—I think not—but the apple falls because it is forced to fall.
Pa. Right! Some force out of itself acts upon it, otherwise it would remain for ever where it was, notwithstanding it were loosened from the tree.
Lu. Would it?
Pa. Undoubtedly! for there only two ways in which it could be moved; by its own power of motion, or the power of something else moving it. Now the first you acknowledge it has not; the cause of its motion must therefore be the second. And what that is was the subject of the philosopher’s inquiry.
Lu. But everything falls to the ground as well as an apple, when there is nothing to keep it up.
Pa. True—there must therefore be a universal cause of this tendency to fall.
Lu. And what is it?
Pa. Why, if things out of the earth cannot move themselves to it, there can be no other cause of their coming together than that the earth pulls them.
Lu. But the earth is no more animate than they are: so how can it pull?