On Automata, or Self-Moving Machines

opportune. Now, it might be doubted for what reason these machines are given the title of self-moving, more so than the cart that is pulled by horses, or the mill that is moved by water; for it is thus that in the self-moving the counterweight acts as the horse does in carts and the water in mills, since the horse and the water move by themselves no less than do the millet and the sand falling from the opening of the pipes, or the counterweight itself toward the center. To this doubt one may respond in two ways: first, because the horse is not a part of the cart, except in a broad sense, nor the water of the mill, whereas the counterweight is a part of the machine. Whence it follows that, the horse and the water being external principles, it cannot be said that those machines move by themselves, but rather that they are moved by something outside of them; for he who speaks of a thing that moves places the principle of motion within the thing that moves, whereas he who speaks of a thing moved places the mover—that is, the principle of motion—outside the thing moved. The other reason, and perhaps a better one, is that in the cart and the mill, the movers are manifest—namely, the horse and the water—wherefore, being seen by all, it cannot enter into anyone's mind that those machines move by themselves. This does not occur in these self-moving ones, in which the principle of motion, which is the counterweight, remains hidden and seen by no one. That this second reason is sound is argued by the fact that Hero wished to warn us that the machines should be made so small that it cannot enter the minds of the spectators that there might be a person within who moves them; as if he meant to say that if it should occur to the mind of the viewer that a man could be contained within to move them, once the mover was known, the wonder would cease, as would the reason for calling them self-moving. Nonetheless, it might