Chapter 11

23 Epicurus introduced this account because he feared that if the atom were always carried along by its natural and necessary weight, we would have no freedom: the mind would move as the motion of the atoms compelled it. Democritus, the originator of the atomic theory, preferred to accept this—that everything happens by necessity—rather than strip indivisible bodies of their natural motions. Carneades took a shrewder course. He taught that the Epicureans could defend their position without this invented swerve. Since they maintained that there could be a voluntary movement of the mind, they would have done better to defend that than to introduce a swerve for which, above all, they could discover no cause. Once they had defended this, they could readily resist Chrysippus. For in granting that there is no motion without a cause, they need not grant that everything that happens happens through antecedent causes: our will has no external, antecedent causes.

24 We thus stretch the ordinary usage of language when we say that someone wants or does not want something without a cause. By “without a cause” we mean without an external, antecedent cause, not without any cause at all. When we call a vessel empty, we are not speaking as the natural philosophers do, for whom ‘empty’ means containing nothing whatever; we mean, for example, that the vessel contains no water, wine, or oil. So too, when we say that the mind moves without a cause, we mean that it moves without an antecedent, external cause, not altogether without a cause. The atom itself may be said to move without a cause when it travels through the void by its own gravity and weight, since no cause acts on it from outside.

25 Yet again, lest all the natural philosophers laugh at us for saying that anything happens without a cause, we must draw a distinction. We must say that it is the nature of the indivisible body itself to move by weight and gravity, and that this very nature is the cause of its moving as it does. Likewise, no external cause need be sought for the mind’s voluntary movements. Voluntary movement contains within itself the nature that makes it lie in our power and obey us; nor is this without a cause, for its very nature is the cause of that.

23 Here is why Epicurus came up with this account. Suppose an atom's weight always carried it along in a natural, unavoidable way. The movement of atoms would then force our minds to move as they did. Epicurus feared that this would leave us no freedom. Democritus, the originator of the atomic theory, chose the other option. He accepted necessity as the explanation of everything, rather than strip indivisible bodies of their natural movements. Carneades took a more perceptive approach. In his teaching, the Epicureans could make their case without inventing a swerve. They held that a movement of the mind could be voluntary. Defending that position was the better course. Why bring in a swerve, particularly when they could find no cause for it? Defending voluntary movement would let them answer Chrysippus easily. They could accept a cause for every movement and still reject preceding causes as the explanation of everything that occurs. Our will, on this account, does not have causes outside itself that come before it.

24 Our everyday way of speaking is loose, then, when we say that someone wants something, or does not want it, “for no reason.” In saying “for no reason,” we mean that there is no outside cause coming first. We do not mean that there is no cause of any sort. Take the way we call a container empty. We do not mean what the students of nature mean: for them, a void has nothing in it. We mean, for instance, a container without water, wine, or oil. It is the same when we speak of the mind moving “without a cause.” We are denying a cause outside it and prior to it, not denying all causes. Even an atom could be said to travel causelessly through the void as its own heaviness and weight carry it along. No cause from outside comes into play.

25 Still, we must distinguish the senses. Otherwise every student of nature will laugh at us for allowing a causeless event. We should put it this way. Movement by heaviness and weight belongs to the very nature of an indivisible body. That nature itself explains why the body travels in that fashion. Apply the same point to voluntary mental movements: there is no need to seek a cause outside them. What makes a movement voluntary is its own nature, which makes it answer to us and leaves us in charge of it. This is not causeless either. The cause is precisely that nature.