EATING PEOPLE IS WRONG. But why? People of different sorts, at different times, expressing their views in different idioms, have had different answers to that question. Right now, our culture isn’t obsessed with cannibalism, though we are still unwholesomely fascinated enough to buy books and go to movies about anthropophagy among the Uruguayan rugby team that ran out of food after their plane crashed in the Andes; or about “the Milwaukee cannibal,” Jeffrey Dahmer; or Armin Meiwes’s successful, internet-mediated search for a voluntary victim (and meal) in Germany in 2001; or, most famously, about the (still controversial) dietary practices of the Donner party stranded in the Sierra Nevada mountains in 1846.

Our modern idioms for disapproving of cannibalism are limited. There is a physical disgust at the very idea of eating human flesh, though it’s not clear that this is necessarily different from the revulsion felt by some people confronted with haggis, calf brains, monkfish liver, or sheep eyes, the rejection of which rarely requires, or receives, much of an explanation. It is widely thought that cannibalism is in itself a crime, but in most jurisdictions it isn’t. (It is criminal to abuse a corpse, so eating dead human flesh tends to be swept up under statutes mainly intended to prevent trading in human body parts or mutilating cadavers.)

Modern condemnations of cannibalism largely set aside questions of moral law or natural law, with their suppositions about the nature of human beings, and thus what is unnatural. These are not assumptions we’re comfortable with these days; chacun à son goût is more to our taste. Formal prosecutions of modern anthropophagists — when they happen — now fasten on attendant crimes, notably, though not necessarily, murder. Cannibalism can be judged a sign of insanity, and the perpetrator locked up not for a criminal act but for mental derangement likely to endanger himself or the community. In 1980, the Poughkeepsie, New York, murderer and testicle-eater Albert Fentress was found not guilty by reason of insanity and committed to a psychiatric hospital. The more famous, but less real, Dr. Hannibal (“the Cannibal”) Lecter was confined to a state hospital for the criminally insane. The cannibal is less and less an actor in the sciences of human nature and culture, more and more handed over to the criminologist, the psychopathologist, and the journalist. The figure of the cannibal is good for selling books and movie tickets, but not particularly important to think about or to draw lessons from.

But it hasn’t always been this way: Cannibalism was once taken very seriously indeed, and the Romanian philosopher Catalin Avramescu’s learned and brilliantly told intellectual history of anthropophagy recovers the cannibal’s once central place in formal thought about what it means to be human. Commentators from antiquity through at least the 18th century needed first to establish whether cannibalism actually existed as a collective practice. Everyone knew of spectacular acts of individual cruelty littering the historical record and popu...