And the tenth is the command respecting all lusts. As, then, he who entertains unbecoming desires is called to account; in the same way he is not allowed to desire things false, or to suppose that, of created objects, those that are animate have power of themselves, and that inanimate things can at all save or hurt. And should one say that an antidote cannot heal or hemlock kill, he is unwittingly deceived. For none of these operates except one makes use of the plant and the drug; just as the axe does not without one to cut with it, or a saw without one sawing with it. And as they do not work by themselves, but have certain physical qualities which accomplish their proper work by the exertion of the artisan; so also, by the universal providence of God, through the medium of secondary causes, the operative power is propagated in succession to individual objects.