AS RECENTLY as two or three years ago polite opinion tended to associate pornography with the freedoms of expression and the nobler aspirations of mankind. Although divided between those who honestly approved of pornography and those who felt obliged to defend it in the name of civil liberty, the opinion was sufficiently respectable to serve as a proof of moral enlightenment. In advanced circles any gentleman author who prided himself on the quality and expense of his sensibility signed, unthinkably and almost as a matter of routine, petitions on behalf of pornographers in trouble with the police. The signature testified to an alliance with the First Amendment, and a sympathy for political dissidents rotting in totalitarian jails.

The sentiment had been stocked in the intellectual inventory during the expansionist programs of the 1960s when Hugh Hefner, revolving on his round bed among pornographic mannequins in Chicago, promulgated the "Playboy Philosophy" and when it was widely believed that prurience was another name for art.

Toward the end of the 1970s the conventions of permissiveness lost something of their charm. The soft, gauze-colored pornography of the previous decade became increasingly ugly, and it was noticed that the American traffic is smut yielded an annual profit larger than the combined earnings of the film and record industries. Pornography had become big business; more often than not the product was as nasty as the toxic wastes dumped into the Love Canal.

The response to this discovery took almost as many forms as there were voices to give expression to the news that something had gone wrong with the dream of flowers. Mustering under the banners of neo-conservatism, Right-to-Life and Moral Majority, the constituencies on the political right joined together in a moral crusade that eventually provided Ronald Reagan with a political campaign. The apologists for these creeds announced a return to the old ways and the old values. They subjected the current definitions of liberty to cross-examination and tried to make the prosecution's case that what the 1960s had meant by personal freedom was little more than an excuse for selfishness and exploitation.

Among the constituencies of the left the militant feminists seized upon the evidence of pornography as the most violent proof of the male conspiracy that had held them in bondage for 6,000 years. The two books under review extend the feminist complaint into reaches of nihilism.

Both Andrea Dworkin and Susan Griffin assume the personae of revolutionaries, and they write the rhetorical prose of political insurgency. They conceive of men as an imperial state. The sovereign sex rules the capitals of culture, and its legions go forth to lay waste the provinces of women. All things bright and beautiful succumb before the terrible advance of the pornographic image. Sexual feeling lies raped and dying on the road; children turn into stone; Dionysius retreats into the sacred grove; civilization murders eros, and those unhappy women who survive the massacre drag out their lives as slaves.

The political specifications do less harm to Dworkin's book. She means to write a manifesto, and within the first few pages of Pornography she anounces her intention to overthrow the seven pillars of what she calls "male supremacist ideology." These she lists as the powers of self, strength, terror, naming, owning, money and sex. Men command all these powers; women command none of them, and therein lies the burden of Dworkin's heavy song. She quotes at length from works of low pornographic fiction as well as from more reputable literary and psychoanalytic sources, but she deploys the words as if they were blunt instruments, and she seems to take pleasure in the recitation of obscenity. Her audience presumably consists of feminist guerrillas still holding out behind enemy lines.

Susan Griffin writes with more subtlety and control. Pornography and Silence convincingly dissects the dehumanizing character of pornography. Against those who would align it with the love of life and the human body, Griffin argues that pornography constitutes an expression of fear, hatred and the wish to annihilate the self. Extending her argument by means of historical as well as metaphysical example, she defines pornography both as a weapon and a drug and associates it not only with the brutality of organized religion but also with the sophistries of racism and with the mass murder committed by Nazis. Like the priest, the slaveholder and the SS officer, the pornographer must conceive of his victim as something other than himself, a being not quite human. The transformation of a woman into an object allows the pornographer to play at being God. This murderous delusion obliges the poor fool to deny the consciousness of feeling. Together with his victim the pornographer becomes less than human, an impersonation of a self who can say, when later examined by the judges at Nuremberg, that he carried out his orders because he had lost an identity that he could recognize as his own.

In her compassionate moments Griffin sees in the pornographic image not only the lineaments of feminine humiliation but also a portrait of human grief and loss that comes to men as well as to women. In this larger perception pornography stands revealed as cruel artifice made by mutilated children trying to explain to themselves their emotional dismemberment.

So far, so good, and it would have been a kindness to the reader if Griffin had resisted the temptation to make of her observations a political theory. But her thesis insists that culture, in all its forms, is, by definition, pornographic. To support this dogma, she makes so many doubtful statements (to the effect that culture ignores women, that women tend inevitably to subservience) that her more useful remarks about the nature of pornography lose their force and urgency. For the purposes of her polemic, Griffin defines cultures as anything that gets in the way of ecstasy. All law, all thought, all power -- all these achievements of the human spirit represent to Griffin aspects of the masculine plot to suppress women. The feminine gender she equates with Mother Nature. Mother Nature, as Rousseau and Dionysius knew, embodies all the good and sweet things of the earth, and these Griffin variously identifies as innocence, frenzy, mysticism, erotic feeling (unimpaired by images), wholeness, lesbianism, reality, Buddhism, darkness, the mythologies of the American Indians and the bliss beyond speech.

Griffin thus ends almost as ominously as Dworkin. Both writers talk about the importance of human feeling, but, like their ideological allies on the political right, they give little evidence of knowing what the words mean. They write almost entirely in abstractions, and they draw their examples from libraries, not from the leaf mold of life and experience. Their obsession with pornography hints at an almost voluptous contemplation of the power they say they despise, and their contempt for a woman's weakness and nonentity would have done credit to the Marquis de Sade.