10.3 The what, how, and why of "free will": A metaphysical digression—Part 3. Why "free will"?

Another set of questions concerns the purpose of the sense of free will—how did it enhance biological adaptation? Metaphysicians who agree free will is illusion divide on whether the illusion is necessary, and a popular view holds that if they truly came to believe determinism, humans would have no reason to act. This view is espoused by some deterministic free-will deniers, not only antideterminist "libertarians," but as you'd expect, the libertarians express the strongest views; one libertarian social psychologist claims to have demonstrated experimentally that college-student subjects cheat more on tests after they're induced to disbelieve in free will. Simply put, his theory is that if we deny our behavioral origination we have less drive to behave responsibly. If this psychological claim is true, the semblance of a motivational push to do the right thing is adaptive, and bearing ultimate responsibility for deeds supplies the evolutionary pressure favoring the free-will experience. But the assumption that perceived free will is adaptive doesn't explain how this perception motivates. Phenomenally, it seems to explain motivation it purports to provide—because the appearance that free will motivates results inexorably from the free-will experience itself: when you experience your behavior as deriving from the perception that your mental states immediately cause acts, you will reasonably conclude that subtracting this (nonexistent) push undermines motivation and responsibility.

The present theory better explains apparent natural selection for this form of purely mental causation. When decision produces action, the actor's nervous system must register that the decision—the actual decision, not the experience of deciding—caused the act, to enable the actor to distinguish voluntary acts from involuntary movements. Coupling a sense of deciding with the decision, by placing the phenomenal deciding experience where the actor relates it to what follows, conveys this information. The "free will," then, is a byproduct of other evolutionary design choices.

What about the finding that free will is more conducive to honesty than determinism? Consider the mental operations of a subject induced to believe determinism is true in a psychology experiment. The subject can't rid himself of free will or even weaken its grip by another "freely willed" act! Whether it's possible to experience oneself in a purely deterministic fashion is itself a debate; Buddhism, for example, seeks to promote this loss of sense of free will (along with other baggage), but the transformation is a long-term project, not the intellectual recognition that determinism is true. The subjects' thoughts elicited by the faux-determinist propaganda delivered in the experimental condition are futile for overcoming the subjects' sense they have free will. At most, the subjects can negate specific attitudes they attribute to their supposed free will: I eschewed cheating because free will made me feel I'm the originator of my acts. Having learned I'm not the originator, I have no continuing reason to abstain from dishonest practices I previously shunned, when my ersatz sense of origination suckered me. Therefore, I should disregard the apparent demands of the autonomous will by behaving less honestly. Subjects can suppress only specific impulses and inhibitions they had previously justified by libertarianism; the subject hopes to avoid being a free-will sucker, despite continuing to experience the false sense of free will. The subject now "freely wills" the new behavior, while willfully suppressing what had once been "freely willed."

Neither the societal effects of disillusion with libertariansm nor the individual effects are apt to be straightforward.