In his autobiography John Stuart Mill confided that, among his other youthful worries, “the doctrine of what is call Philosophical Necessity weighed on my existence like an incubus. I felt as if I was scientifically proved to be the helpless slave of antecedent circumstances; as if my character and that of all others had been formed for us by agencies beyond our control, and was wholly out of our own power.” Mill was not alone in fretting about free will. At the other end of the intellectual universe, Dostoyevski’s Underground Man agreed: “What is a man without desires, without free will and without choice, if not a stop in an organ?” In fact, as Daniel Dennett reports in “Elbow Room”, it’s been plausibly claimed that more has been written on free will than on any other philosophical topic. And to judge from his citations, the topic is still a live one. Clearly philosophers, at least, have not gotten beyond freedom and dignity.

Dennett is one of the most interesting contemporary American philosophers. His “Brainstorms” (1978) was a state-of-the-art collection of essays on philosophy of mind, full of bravura argumentation and illuminating excursions into psychology, physiology, and computer science. “The Mind’s I” (1981), co-edited with Douglas Hofstadter (author of “Godel, Escher, Bach”) was a popular anthology of classics and curiosa. “Elbow Room” is the 1983 John Locke Lectures at Oxford, where Dennett learned analytic philosophy from Gilbert Ryle and many of its other creators.

“Brainstorms” laid out the “free will problem” in technical terms: “(1) How can a material thing (a mechanism?) be correctly said to reason, to have reasons, to act on reasons? (2) How can the unique four-dimensional non-branching world-worm that comprises all that has happened and will happen admit of a notion of possibilities that are not actualities? What does an opportunity look like when the world is viewed sub specie aeternitatis? (3) How can a person be the author of decisions and not merely the locus of causal summation for external influences? (4) How do we make sense of the intuition that an agent can only be responsible if he could have done otherwise? (5) How can we intelligibly describe the relevant mental history of the truly culpable agent—the villain or rational cheat with no excuses? As Socrates asked, can a person knowingly commit evil?” “Elbow Room” is an elegant but less technical treatment of these and other tricky questions—how does a self happen? what does “can” mean? what is the moral status of luck? is anyone to blame for anything? why do we want free will, anyway?

Like most Anglo-American philosophers, Dennett is a naturalist, a physicalist, and a determinist (these are overlapping terms). He believes that we think with our brain and nervous system; that ideas, volitions, and other abstract entities are useful (some times mischievous) fictions; that, as his mentor, Ryle, put it, there is no “ghost in the machine” (i.e., immaterial mind or soul); and that, as his adversary Skinner put it, “there is only one world, the world of physics,” subject to physical laws. Yet he also believes that we have free will, in some sense worth wanting. Disentangling that sense from the thicket of illogic and superstition that surrounds it is a delicate business and involves Dennett in an argument so intricate that it comes to resemble a narrative.

Dennett first tells a story of how reflective intelligence may have evolved from tropism and instinct. At crucial stages in evolution, perceptual cascades induce iteration processes and feedback loops, which establish representational hierarchies and metalanguages, which are the main components of “semantic engines”—i.e., minds. Mercifully, Dennett explains all this: our thickening web of perceptions and interests calls for new behavioral strategies, which are achieved (perhaps accidentally) by applying “whatever tricks one has to one’s existing tricks.” Or in an older language that Dennett does not use, quantity becomes quality.

Once an organism can deliberate about reasons, we can define free will as the extent to which those deliberations are effectual and uncoerced. Most of “Elbow Room” is devoted to showing why this definition does not imply, on one hand, that our choices are uncaused, or on the other, that we are prisoners in a deterministic universe. Between the Scylla of fatalism and the Charybdis of theology, Dennett navigates his philosophical bark home to the port of common sense. We’re free, within limits—just as we always thought, or at least assumed in practice.

Actually, what Dennett ends up with is common sense refined, deepened, and nudged ever so gently toward humane, engaged rationality. Analytic philosophy is a little like Zen wisdom: the landscape looks the same afterwards, only we can concentrate better. Having exorcised Mill’s incubus and other philosophical demons, Dennett concludes with a hint: “There are real threats to human freedom, but they are not metaphysical.”