In a passage quoted in the last post, Jerry Coyne claims that quantum indeterminacy is irrelevant to free will: “Even the pure indeterminism of quantum mechanics can’t give us free will, because that’s simple randomness, and not a result of our own ‘will.'”

Coyne seems to be thinking that since quantum indeterminism has fixed probabilities in any specific situation, the result for human behavior would necessarily be like our second imaginary situation in the last post. There might be a 20% chance that you would randomly do X, and an 80% chance that you would randomly do Y, and nothing can affect these probabilities. Consequently you cannot be morally responsible for doing X or for doing Y, nor should you be praised or blamed for them.

Wait, you might say. Coyne explicitly favors praise and blame in general. But why? If you would not praise or blame someone doing something randomly, why should you praise or blame someone doing something in a deterministic manner? As explained in the last post, the question is whether reasons have any influence on your behavior. Coyne is assuming that if your behavior is deterministic, it can still be influenced by reasons, but if it is indeterministic, it cannot be. But there is no reason for this to be case. Your behavior can be influenced by reasons whether it is deterministic or not.

St. Thomas argues for libertarian free will on the grounds that there can be reasons for opposite actions:

Man does not choose of necessity. And this is because that which is possible not to be, is not of necessity. Now the reason why it is possible not to choose, or to choose, may be gathered from a twofold power in man. For man can will and not will, act and not act; again, he can will this or that, and do this or that. The reason of this is seated in the very power of the reason. For the will can tend to whatever the reason can apprehend as good. Now the reason can apprehend as good, not only this, viz. “to will” or “to act,” but also this, viz. “not to will” or “not to act.” Again, in all particular goods, the reason can consider an aspect of some good, and the lack of some good, which has the aspect of evil: and in this respect, it can apprehend any single one of such goods as to be chosen or to be avoided. The perfect good alone, which is Happiness, cannot be apprehended by the reason as an evil, or as lacking in any way. Consequently man wills Happiness of necessity, nor can he will not to be happy, or to be unhappy. Now since choice is not of the end, but of the means, as stated above (Article 3); it is not of the perfect good, which is Happiness, but of other particular goods. Therefore man chooses not of necessity, but freely.

Someone might object that if both are possible, there cannot be a reason why someone chooses one rather than the other. This is basically the claim in the third objection:

Further, if two things are absolutely equal, man is not moved to one more than to the other; thus if a hungry man, as Plato says (Cf. De Coelo ii, 13), be confronted on either side with two portions of food equally appetizing and at an equal distance, he is not moved towards one more than to the other; and he finds the reason of this in the immobility of the earth in the middle of the world. Now, if that which is equally (eligible) with something else cannot be chosen, much less can that be chosen which appears as less (eligible). Therefore if two or more things are available, of which one appears to be more (eligible), it is impossible to choose any of the others. Therefore that which appears to hold the first place is chosen of necessity. But every act of choosing is in regard to something that seems in some way better. Therefore every choice is made necessarily.

St. Thomas responds to this that it is a question of what the person considers:

If two things be proposed as equal under one aspect, nothing hinders us from considering in one of them some particular point of superiority, so that the will has a bent towards that one rather than towards the other.

Thus for example, someone might decide to become a doctor because it pays well, or they might decide to become a truck driver because they enjoy driving. Whether they consider “what would I enjoy?” or “what would pay well?” will determine which choice they make.

The reader might notice a flaw, or at least a loose thread, in St. Thomas’s argument. In our example, what determines whether you think about what pays well or what you would enjoy? This could be yet another choice. I could create a spreadsheet of possible jobs and think, “What should I put on it? Should I put the pay? or should I put what I enjoy?” But obviously the question about necessity will simply be pushed back, in this case. Is this choice itself determinate or indeterminate? And what determines what choice I make in this case? Here we are discussing an actual temporal series of thoughts, and it absolutely must have a first, since human life has a beginning in time. Consequently there will have to be a point where, if there is the possibility of “doing A for reason B” and “doing C for reason D”, it cannot be any additional consideration which determines which one is done.

Now it is possible at this point that St. Thomas is mistaken. It might be that the hypothesis that both were “really” possible is mistaken, and something does determine one rather than the other with “necessity.” It is also possible that he is not mistaken. Either way, human reasons do not influence the determination, because reason B and/or reason D are the first reasons considered, by hypothesis (if they were not, we would simply push back the question.)

At this point someone might consider this lack of the influence of reasons to imply that people are not morally responsible for doing A or for doing C. The problem with this is that if you do something without a reason (and without potentially being influenced by a reason), then indeed you would not be morally responsible. But the person doing A or C is not uninfluenced by reasons. They are influenced by reason B, or by reason D. Consequently, they are responsible for their specific action, because they do it for a reason, despite the fact that there is some other general issue that they are not responsible for.

What influence could quantum indeterminacy have here? It might be responsible for deciding between “doing A for reason B” and “doing C for reason D.” And as Coyne says, this would be “simple randomness,” with fixed probabilities in any particular situation. But none of this would prevent this from being a situation that would include libertarian free will, since libertarian free will is precisely nothing but the situation where there are two real possibilities: you might do one thing for one reason, or another thing for another reason. And that is what we would have here.

Does quantum mechanics have this influence in fact, or is this just a theoretical possibility? It very likely does. Some argue that it probably doesn’t, on the grounds that quantum mechanics does not typically seem to imply much indeterminacy for macroscopic objects. The problem with this argument is that the only way of knowing that quantum indeterminacy rarely leads to large scale differences is by using humanly designed items like clocks or computers. And these are specifically designed to be determinate: whenever our artifact is not sufficiently determinate and predictable, we change the design until we get something predictable. If we look at something in nature uninfluenced by human design, like a waterfall, is details are highly unpredictable to us. Which drop of water will be the most distant from this particular point one hour from now? There is no way to know.

But how much real indeterminacy is in the waterfall, or in the human brain, due to quantum indeterminacy? Most likely nobody knows, but it is basically a question of timescales. Do you get a great deal of indeterminacy after one hour, or after several days? One way or another, with the passage of enough time, you will get a degree of real indeterminacy as high as you like. The same thing will be equally true of human behavior. We often notice, in fact, that at short timescales there is less indeterminacy than we subjectively feel. For example, if someone hesitates to accept an invitation, in many situations, others will know that the person is very likely to decline. But the person feels very uncertain, as though there were a 50/50 chance of accepting or declining. The real probabilities might be 90/10 or even more slanted. Nonetheless, the question is one of timescales and not of whether or not there is any indeterminacy. There is, this is basically settled, it will apply to human behavior, and there is little reason to doubt that it applies at relatively short timescales compared to the timescales at which it applies to clocks and computers or other things designed with predictability in mind.

In this sense, quantum indeterminacy strongly suggests that St. Thomas is basically correct about libertarian free will.

On the other hand, Coyne is also right about something here. While it is not true that such “randomness” removes moral responsibility, the fact that people do things for reasons, or that praise and blame is a fitting response to actions done for reasons, Coyne correctly notices that it does not add to the fact that someone is responsible. If there is no human reason for the fact that a person did A for reason B rather than C for reason D, this makes their actions less intelligible, and thus less subject to responsibility. In other words, the “libertarian” part of libertarian free will does not make the will more truly a will, but less truly. In this respect, Coyne is right. This however is unrelated to quantum mechanics or to any particular scientific account. The thoughtful person can understand this simply from general considerations about what it means to act for a reason.