Harris was a philosophy major at Stanford, but he is inclined to scant most of what philosophers have had to say about well-being. There is, for example, a movement in contemporary philosophy and economics known as “the capabilities approach,” which takes seriously the question of identifying the components of well-being and measuring them. But neither of the two leading exponents of this approach — the philosopher and economist Amartya Sen and the philosopher and classicist Martha Nussbaum — gets a mention in the book.

The most compelling strand in “The Moral Landscape” is its unspooling diatribe against relativism. Harris insists that there are correct answers to all questions of right and wrong, regardless of anyone’s culture or religion. And, though some questions may escape our inquiries, many can be answered by science; none, he appears to think, can be answered without it.

You might suppose, reading this book, that this anti-relativism was controversial among philosophers. So it may be worth pointing out that a recent survey of a large proportion of the world’s academic philosophers revealed that they are more than twice as likely to favor moral realism — the view that there are moral facts — than to favor moral anti-realism. Two thirds of them, it turns out, are also what we call cognitivists, believing that many (and perhaps all) moral claims are either true or false. And Harris himself concedes that few philosophers “have ever answered to the name of ‘moral relativist.’ ” Given that, he might have spent more time with some of the many arguments against relativism that philosophers have offered. If he had, he might have noticed that you can hold that there are moral truths that can be rationally investigated without holding that the experimental sciences provide the right methods for doing so.

Still, there’s plenty of interest in “The Moral Landscape.” Harris draws our attention to the fact that “science increasingly allows us to identify aspects of our minds that cause us to deviate from norms of factual and moral reasoning.” And when he stays closest to neuroscience, he says much that is interesting and important: about the limits of functional magnetic resonance imaging as a tool for studying brain function; about the current understanding of psychopaths (whose brains display “significantly less activity in regions of the brain that generally respond to emotional stimuli”); about the similarities in the ways in which moral and nonmoral belief seem to be handled in the brain. I found myself wishing for less of the polemic against religion, which recurs often and takes up one entire chapter — he has had two bites of that apple already, and will soon be reduced to gnawing at the core — and I wanted more of the illumination that comes from our increasing understanding of neuroscience.

Yet such science is best appreciated with a sense of what we can and cannot expect from it, and a real contribution to the old project of a “naturalized ethics” would have required a fuller engagement with its contradictions and complications. Instead, the landscape that the book calls to mind is that of a city a few days after a snowstorm. A marvelously clear avenue stretches before us, but the looming banks to either side betray how much has been unceremoniously swept aside.