The terrorist has been a familiar figure in pop mythology for practically all of this benighted century. He began, in newspaper cartoons, almost as a figure of fun -- a small man, heavily bearded, carrying a bomb that looked like a bowling ball with a wick coming out of it. In the last generation, terrorism and extortion have become a historic leitmotif, and the image of the terrorist has evolved in the popular imagination to resemble Che Guevara, Yasser Arafateven, most remarkably, Patricia Hearst

In "Proteus," Morris West brings out some relatively overlooked aspects of terrorism. He points out that governments have been the largest and most successful agents of terror in our time, and he introduces to the public mythology a new kind of terrorist: a middle-aged man, wealthy, dressed in a tailored business suit, carrying a briefcase and saying unspeakable things in a soft, well-modulated voice.

West's new-style terrorist is John Spada, 55, of New York, president of a multinational corporation and also of a secret but benign international organization called Proteus. The story of how he is driven to blackmail an entire planet is a harrowing one, not quite so incredible as the reader might wish, and it confronts head-on one of the most agonizing moral dilemmas of our time. It is told with more clarity than elegance, but this is expected of the author, whose novels tend to be interesting for their ideas rather than their style.

The basic idea in "Proteus" is one that has become almost self-evident in the last few generations: that the lowest common denominator is becoming the norm in many situations of public conflict -- that the rule of law, reason and traditional moral systems is yielding to a near-spasmodic system of threat and counterthreat. The corollary is that a decent human being trapped in this dialectical process has no option, short of surrender, except to become like his adversary, to adopt tactics that he despises for the sake of survival.

Historically, the process was shown in World War II when the United States put some of its own citizens in concentration camps as part of its struggle against Japan, and later when a system of informants, loyalty tests and secret dossiers was set up to combat Stalinism. West puts the same dilemma in a more personal and contemporary context in the words of Hugo von Kalbach, a German philosopher who has just written a book called "The Phenomena and Epidemiology of Violence," and who will be killed by a terrorist in the course of the novel:

"We are all familiar with the phenomena, the things that happen: assassination, hijacking, bombing, the violence practiced by police, by security men, by professional torturers... It is our response which is in question. How far can we go? What morality applies?... I have written not an answer but a riddle: 'If I act, I become one of them. If I act not, I become their slave.'"

Later, after Spada's daughter and her husband (a crusading journalist) are imprisoned and tortured by the government of Argentina, Von Kalbach answers his own riddle: "There is no way to bargain with evil. You have to fight it -- even to death." And this is what John Spada finally does, with a gesture that is ultimately as futile as it is spectacular. He develops a bacteriological weapon, arms members of the Proteus organization with it and threatens to unleash it against the population of the world unless all governments holding politicall prisoners set them free.

The aftermath is more realistic than this dramatic twist of the plot: stormy rhetoric in the United Nations, cool calculations of "acceptable" casualty figures, quibbling and offers of token compliance. Ultimately, Spada accepts defeat and commits suicide, because although he can make noises like a terrorist ("I'm a civilized man, for Christ's sake, and in half a year they've stripped me naked, back to barbarism. Now they'll contend with the beast they've made!"), he is not one at heart. A true terrorist would have unleashed his weapon, finding in death and chaos the true vindication and satisfaction he has been seeking.

Like von Kalbach, West has written not an answer but a riddle; the problem he faces is not technical but moral, and his answer is not hard to find, only to accept. It is that if we are to survive in a world of terrorism we will inevitably have to descend to the level of the terrorists -- or, at best, delegate such a role to some part of our government. There may be some comfort in the fact that the author clearly finds this answer as unacceptable as most readers will find it. But I'm afraid it's small comfort.