When the behavior of organisms is concerned, the lawful mechanisms are conventionally categorized into those that operate from the inside and those that operate from the outside. Biologist Anthony Cashmore recently put it this way: Behavior is the result of "a trinity of forces," namely "genes, environment, and stochasticism" (i.e., chance; from the Greek word for guessing). What else is there? Cashmore argues that to assume the existence of free (uncaused) will is to assume the existence of a magical cause, that is, a cause that springs from nothing. To ensure that free will is independent from brain processes, it must be located beyond the physical world encased by the cranium, so Cashmore. Hence, the idea of free will requires a dualist philosophy, which allows non-physical systems to act on the physical world. Belief in free will is philosophically the same as belief in a soul that is independent of the body.
Most advocates of free will do not deny most of the universe's (and the brain's) deterministic machinery. They rather believe that unless mechanistic science explains everything, there is room for free will. Notice that this argument does not refute soft determinism because soft determinism allows for irreducible uncertainty arising from chance. In other words, belief in free will is compatible with (soft) determinism.
Or is it? Like any belief that wants to be part of the scientific conversation, the belief in free will must have a foundation that is broader than mere faith. The problem is that free will requires irreducible unpredictability, which makes it tough to distinguish from chance. The burden is on those who believe in free will to show how freely willed behavior can be distinguished from random behavior. I am aware of no successful attempt to do so.
What we have instead is the subjective feeling that a behavior is freely willed. This feeling can be quite powerful, but it is easily mistaken. Suppose I have a choice between watching a movie with Cecile de France and watching a documentary on basket weaving in the Mato Grosso. I enthusiastically choose the former and claim that I am doing so freely. No one is holding a gun to my head, after all. Indeed, my choice is intentional because I have a desire to see Cecile and I am terribly indifferent about baskets. Intentionality does not presuppose freedom, however. I am comfortable with the idea that my desire to see Cecile is fully determined by my genetically and environmentally shaped schemas of attractive people. Every time we make a choice forcefully, confidently, and comfortably, it is easy to construct a causal account using pre-existing preferences that match the properties of the stimulus. We should want it to be so for without preferences and other features of our character how could we maintain a sense of identity? A perfectly free person would have no personality.
Now consider a choice between watching a documentary on basket making in the Mato Grosso and a documentary on basket-making in lower Patagonia. This shapes up to be a yawn for someone like me. There is no strong preference either way. Yet, I have to choose [if I am denied the freedom not to choose, even this scenario has its own constraints]. I could toss a physical coin and let randomness decide or I could toss a mental coin [remember the dice man]. It is hard, if not impossible, to mentally simulate randomness. Perhaps it is here that I can lay a claim for free will. But even if so, it would be the kind of free will least worth having. It would be the freedom to choose among options that we do not care about. Think of the child that wants the chocolate pudding, whereas the parents offer a choice between broccoli and spinach. The choice the child cares about is determined by the physiology of desire.
What if desire favors both options? Say you have a choice between going out with Brad, who is rich and handsome, and going out with George, who is loyal and who enjoys discussing his feelings. If the pull of both is equally strong, isn't this a perfect opportunity to freely break the decisional gridlock? Perhaps, but notice again the difficulty of ruling out chance or a subtle inequality in the strength of desire. Indeed, when approach - approach conflicts come to a head (figuratively and literally), individuals tend to become distressed. Instead of enjoying the golden opportunity to exercise free will, they want to discover their true preference, the stronger preference, the preference that tells them who they really are. In short, they place their hopes in determinism.
After considering avoidance - avoidance conflicts (basket weaving) and approach - approach conflicts (desirable dates), what's left are approach - avoidance conflicts. Long the subject of behavioral studies, these conflicts are now prominent in the literature on "intertemporal choice" or "discounting." George Loewenstein puts the problem sharply, saying that in the typical conflict pits an immediate, viscerally gratifying reward against a larger but more distant and cerebral reward. Whether an individual yields to temptation must be, in large part, a function of how much desire the immediate reward stokes.
From the perspective of free will, a person is said to have the choice to resist temptation no matter how strong that temptation is. Notice that this is a much stronger claim than the one I introduced earlier. There is no search for a decision region here that is left open by soft determinism. Here, we have the idea that free will can and must trump determinism. In my view, this feature makes the claim a moralistic one. It sets the stage for the disbursement of blame and praise, respectively after yielding to and resisting temptation. This notion treats free will as true by definition. You yield to temptation because you want to; after all, you could decide differently. Hence, you must be blamed. You resist temptation because you want to; you could decide differently. As I enjoy ironies, how about this one: Does it ever occur to moralists to stop blaming the tempters and the tempted? Can they not choose not to blame? Or is it a free will for you but not for the judge?
In approach - avoidance conflicts, we often experience our mental deliberations as hard work. Effortful reasoning is time-consuming, mentally costly, and even painful. We can literally feel the price we're paying, and that price is measured in burnt calories. It is tempting [ ☺ ] to conclude that we engage in this sort of reasoning only out of our own free will. But then again, why freely choose a taxing activity? I rather think that the idea of identifying effortful thinking with free thinking is a derivative of the idea that "If all thinking is the reflection of fully deterministic brain processes, then there is no point why these processes should feel like work," which leads to the conclusion that "If thinking feels like work, it must be free." This conclusion comes from modus tollens [proof by denial] or the negation of the consequent, and it is valid. The question is, of course, whether the original if-then claim is empirically true. Surely, many deterministic processes consume a lot of energy (e.g., turning milk into butter). This means we have no empirical basis to begin with the claim that "If thinking is deterministic, it must be easy."
Consider the logical structure of an alternative argument, an argument that is not undone by the lack of empirical support, an argument that appeals only to subjective experience.
"If there is free will, it will make itself known in our subjective experience (even if that means pain)." However persuasive it may sound (see my response to Baumeister), the then-clause does not entail the if-clause. This would be what a logician might call modus nonsense. We may believe in free will for other reasons than that there is free will. Determinism says that if you believe in free will, there are sufficient causes that make it so (e.g., you heard a lecture by a professor of philosophy who has forgotten Hume).
Perhaps you decide (freely?) to believe in free will to hedge your bets. Edward Lorenz (who came up with the cool butterfly effect) once said (and I paraphrase) "I believe in free will because if free will is true I will have made the right choice; if determinism is true, well, then I couldn't believe otherwise." Note that this is not a proof, but a clever example of applied decision theory, much like Pascal's wager did not prove God's existence but only gave a reason for betting on (er, believing in) it.
Consider the Lorenz situation again as a meta-choice in what to believe in: free will or determinism. If you choose to believe in determinism you can claim that this choice too is determined. To claim that you freely choose to believe in determinism makes no sense. By contrast, if you choose to believe in free will, you need to also claim that this choice is freely willed. To say that it is determined negates the chosen belief. In other words, the choice to believe in free will itself cannot be free. You have to make that choice in order to be coherent, but you cannot be coherent and free at the same time. I assume Lorenz knew these implications. He was just having fun.
That reminds me of another humorous gambit by someone who realized that he could not come up with a proof. William James said that his first act of free will was to declare that he believed in it. Of course, a realist cannot accept the declaration of belief as proof that the belief is true. But James was a pragmatist. He believed that a belief is true if it has desirable consequences. Incidentally, there is some well-publicized research by Vohs, Baumeister and others, which shows that a belief in determinism has some unsavory consequences, such as more cheating. That's too bad, but no proof that free will is true (as the authors note).
Remember that to a proponent of free will, your choice in an approach - avoidance conflict confirms free will irrespective of how you resolve the conflict. The intuitive approach to free will, that is, the idea that you can deduce free will from your own experience, has another, somewhat more sophisticated and more interesting, variant; more interesting and sophisticated because it does allow determinism. According to this view, determinism reveals itself when things go wrong. Problems with speech production, loss of memory, alien hand syndrome, and a host of other neuropsychological impairments are widely recognized as precisely that: deficits arising from neuropsychological lesions or trauma. A lesion in the temporal lobe is readily accepted as the cause of speech loss. When, however, there is no lesion and speech is unimpaired, proponents of free will are ready to withhold credit from the well-functioning lobe. Think of a dog that, because of brain damage, is unable to bark. This does not mean that a dog able to bark freely chooses to do so. Human speech is just more complex than barking, perhaps irreducibly more complex. This is a battle the behaviorists lost, but not the determinists. Do you really believe that you freely choose each word you say? Granted, you can hold words in consciousness before saying them, but that only means that you can speak voluntarily, with intention, but that's another story. It only means that conscious intention can be part of the causal chain (as noted above).
To a determinist, the causal proof is symmetrical. In logical terms, we accept the proposition that if there is a deficit, there is a lesion. By modus tollens, we also accept that if there is no lesion, there is no deficit. In empirical-statistical terms, the lesion/no-lesion distinction is a causal predictor of the deficit/no-deficit distinction. Subjective experience favors free will in the no-lesion state because the physiological mechanisms producing the very experience are out of sight. Instead of proving free will, the deficit-free brain succeeds nicely in generating correlated outcomes (i.e., perceptions, intentions, and action are all in agreement).
The choice examples I have used in this post, ranging from watching basket weaving to eating spinach, were non-social. Much of our most interesting behavior is, however, social. Behavior is social when it is a response to what others have done. Wouldn't a proponent of free will be most interested in having free will in a social situation? Wouldn't it be most rewarding to be free from social influence? But are you? Suppose I say "You are not free to read or not read this post." You might respond "I'll show you and I will not read it." But even your refusal makes my point that you are reacting deterministically. Sir Popper famously called your inability to choose independent of a prediction or a demand the "Oedipus effect." Oedipus, I hope you agree, was the greatest of all tragic Greeks. His fate was determined, yet who would say that he was a lesser human because of it? Indeed, I think the opposite is true. Oedipus's story moves us because it captures the human condition (Aristotle agrees).
I intend this (not so) random walk through the land of the free will to be a primer and also to be an ultimer (how's that for a neologism?). As post number 11 on the topic, I intend it to be the last one - at least until necessity calls and gives me a new intention.
I have no illusions regarding the persuasiveness of this post. If you are a staunch dualist, you will continue to believe that your free will can make your brain do things. Perhaps you are even fortified in your belief because you feel that my approach of telling my side of the story has been sarcastic, dismissive, or plain obnoxious. Take heart! If you are a dualist, stand by your conviction. Be proud of it, and take it seriously. Do what Sidney Friedman does. When you find yourself procrastinating or caving in to base desires, yell at your brain! Says Friedman, "You will raise your voice and yell at your brain. When you are feeling sluggish, or when you are just sitting there on your big ol' butt avoiding doing some task you should be doing, or when you just can't get started organizing your day, or when you are in the midst of something you've started but feel your focus waning, you will yell at your brain.[. . .] So, are you yelling at yourself? No. Be nice to yourself. Never yell at yourself. The brain is a separate entity, while in a manner of speaking, at the same time it's you too."
Heck, there's that sarcasm again. Sorryyyyyyyy!!! I couldn't help it. Stop it, brain! Stop it!
Addendum November 16, 2011:
A new paper in the British Journal of Social Psychology takes the field of social psychology to task for subtely implying that free will is possible because it has not been empirically disproven. Miles (2011) reviews the logical problems of the free will assumption and explores the damage the belief in free will has done to human welfare.
Miles (2011). 'Irresponsible and disservice': The integrity of social psychology turns on the free will dilemma. British Journal of Social Psychology. doi: 1111/j.2044-8309.2011.02077.x
Comic relief: Free will is alive and well in Austria as this store sign in Salzburg proves. 'Frey' means 'free' and 'Wille,' well you know.