How courts have viewed cannibalism; Cannibalism and the Common Law, by A.W. Brian Simpson. Chicago: University of Chicago Press. 353 pp. $25.

Cannibalism is never edifying. Is it ever permissible? Victorian England, apparently, thought it was. ''Cannibalism and the Common Law,'' by legal historian Simpson, is the story of the tragic last voyage of the HMS Mignonette and two sailors who survived by killing a third mate. In 1884, the Mignonette foundered in the South Atlantic, en route to Australia. Capt. Tom Dudley and Edwin Stephens killed their fellow mate Richard Parker in a life raft. Upon their return to England, the two men were tried for murder in a sensational proceeding and sentenced to death. But public opinion, according to Dr. Simpson, was in favor of the men.

The case was hardly a simple one. Cannibalism was then as horrifying to public tastes as it is now. Regina v. Dudley and Stephens became one of the most celebrated trials of Victorian England. The case is still studied as a landmark decision in British and American law.

Simpson mixes his narrative with anecdotes and historical parallels to the case. Since the death sentences for Dudley and Stephens were commuted, Simpson observes, the case showed a great public and legal ambivalence about the morality of the defendants' actions. As Piers Paul Read's book, ''Alive,'' showed, the issue is still not settled.

Simpson's book is not just an intriguing account of a sensational trial. It plumbs to the very heart of the moral and legal questions surrounding the Galtonian idea of survival of the fittest. When survival is at stake, altruism is often the loser to predatory instincts. Emerging in circumstances of extreme physical desperation, expressions of modern cannibalism show us that nature and nurture have at best a fragile truce.