Chance NOT the Direct Cause of Human ActionChance cannot directly cause our actions. We cannot be responsible for random actions. Because of quantum mechanics, we now know that indeterminism is true and absolute chance exists in the universe. Chance can generate random and totally unpredictable alternative possibilities for action, our "Agenda" for the Cogito. These alternatives are generated from our internal knowledge of practical possibilities. Those that are handed up for consideration may be filtered to some extent by unconscious processes to be "within reason." They may consist of slight variations of past actions we have willed many times in the past.
The selection of one of these possibilities by the will is as deterministic and causal a process as anything that a determinist or compatibilist could ask for, consistent with our knowledge of the physical world. Instead of a strict causal determinism, the world offers only adequate determinism. Consequently, at the very most, the indeterminism or chance involved in the generation of alternative possibilities is just an indirect cause of action, and just one of many causes. One of these possibilities is de-liberated by our causally determined will, so we can say that the action was up to us and that we can accept moral responsibility for it.
Some unjustified fears about chance
Through the years, a number of sensible philosophers have panicked at the thought of truly chance events, the dreaded "causa sui." The Stoic Chrysippus warned in the third century B.C.E.
"Everything that happens is followed by something else which depends on it by causal necessity. Likewise, everything that happens is preceded by something with which it is causally connected. For nothing exists or has come into being in the cosmos without a cause. The universe will be disrupted and disintegrate into pieces and cease to be a unity functioning as a single system, if any uncaused movement is introduced into it."Here is P. H. Nowell-Smith's concern about randomness (Mind, volume 225, January, 1948)
The fallacy of [Incompatibilism] has often been exposed and the clearest proof that it is mistaken or at least muddled lies in showing that I could not be free to choose what I do unless determinism is correct. For the simplest actions could not be performed in an indeterministic universe. If I decide, say, to eat a piece of fish, I cannot do so if the fish is liable to turn into a stone or to disintegrate in mid-air or to behave in any other utterly unpredictable manner.J. J. C. Smart is an extreme case of those who believe quantum indeterminism might be a direct cause of action. He is reported to have said:
"Indeterminism does not confer freedom on us: I would feel that my freedom was impaired if I thought that a quantum mechanical trigger in my brain might cause me to leap into the garden and eat a slug."
Examples of Chance the Direct Cause of ActionMany modern philosophers, even libertarians, conclude that if indeterminism is true our actions will be simply a matter of random chance. One of the most influential defenders of libertarianism, Peter van Inwagen, has imagined a situation in which God rewinds the universe to exactly the same circumstances a thousand times. He concludes that an agent will act probabilistically instead of in a way adequately determined by character.
Now let us suppose that God a thousand times caused the universe to revert to exactly the state it was in at t1 (and let us suppose that we are somehow suitably placed, metaphysically speaking, to observe the whole sequence of "replays"). What would have happened? What should we expect to observe? Well, again, we can't say what would have happened, but we can say what would probably have happened: sometimes Alice would have lied and sometimes she would have told the truth. As the number of "replays" increases, we observers shall — almost certainly — observe the ratio of the outcome "truth" to the outcome "lie" settling down to, converging on, some value. We may, for example, observe that, after a fairly large number of replays, Alice lies in thirty percent of the replays and tells the truth in seventy percent of them—and that the figures 'thirty percent' and 'seventy percent' become more and more accurate as the number of replays increases. But let us imagine the simplest case: we observe that Alice tells the truth in about half the replays and lies in about half the replays. If, after one hundred replays, Alice has told the truth fifty-three times and has lied forty-eight times, we'd begin strongly to suspect that the figures after a thousand replays would look something like this: Alice has told the truth four hundred and ninety-three times and has lied five hundred and eight times. Let us suppose that these are indeed the figures after a thousand  replays. Is it not true that as we watch the number of replays increase we shall become convinced that what will happen in the next replay is a matter of chance.Now van Inwagen reveals that he thinks that indeterminism directly results in actions. No wonder on his account that "free will remains a mystery!"