DAMNING THE INNOCENT. A History of the Persecution of the Impotent In Pre-Revolutionary France. By Pierre Darmon. Translated from the French by Paul Keegan. Viking. 234 pp. $18.95.

DAMNING THE INNOCENT isn't quite the right title for Pierre Darmon's curious, mildly prurient little work of pop scholarship. The British edition's title, "Trial by Impotence," is not much better, though it at least makes a stab at translating the French title, "Le Tribunal de l'Impuissance." But what we have here, really, is a book that, with some salutary readjustments, might be labeled "Baroque Sexual Attitudes."

Pierre Darmon's approach to this topic blends historic research with rhetorical outbursts against judges, lawyers and doctors who have been dead for two or three centuries. He often seems personally involved -- affronted by the subject of what should be an objective study. Particularly in the introduction but frequently elsewhere in his text, he attributes motives and attitudes (macho insecurity, prurient curiosity, hatred of women) that may have existed but do not seem adequately documented. He is easier to read (but hardly more scholarly) in his outbursts of sympathy for the victims of religious and governmental strictures that intruded into the most private aspects of married life. And he may be a victim of occasional Freudian slips, as when (in a discussion of impotence) he talks about "pushing the most rigid moral standards to their absolute limit."

His study explores baroque attitudes (specifically Catholic and primarily French) on such sexual anomalies as hermaphroditism and incomplete physical sexual development. Also part of his study are such practices as the marriage of men in their seventies to women in their teens; the mystique of virginity and the prevalence of misogyny among the wielders of power; the meddling of the clergy (particularly confessors) in marital relations; the role of mothers-in-law in disrupting conjugal harmony; and norms for determining the legitimacy of children. He also touches on the evolution of legal and religious views on marriage, which underwent significant change as the Middle Ages yielded to the Renaissance and the body began to claim some of the attention that opinion-leaders had previously lavished on the soul.

But Darmon's primary focus is on the subject of impotence, a topic that assumed overwhelming importance because of the laws on marriage prevailing at that time. In the civil law of Catholic countries (and still today in Catholic canon law), a marriage, once contracted and consummated was eternally indissoluble. It was possible to have it annulled, even after the wedding ceremony, if it could be proven that the couple had not engaged in sexual relations. But after the honeymoon, the only practical way to dissolve a marriage was to prove that the husband (or, more rarely, the wife) was unable to complete a sexual act and therefore the contract had never been fulfilled.

As a result, divorce baroque style became usually a process in which a wife publicly accused her husband of inability to fulfill his husbandly duties. If the husband chose to contest the case (as he might out of pride, not to mention a desire to preserve the marriage), he was obliged to prove to the court's satisfaction that he could function sexually. In the beginning, a husband and wife both eager to dissolve a marriage might agree to corroborate one another's testimony, and the courts, asking no other evidence, would give what amounted to an uncontested divorce. There are cases on record (including a few mentioned in the book) where a man had a marriage dissolved on grounds of impotence, remarried and fathered a large family.

BUT AS TIME passed and doctrine and legal precedents accumulated, the process became more complicated. Impotence, besides carrying a social stigma, could be treated as a crime -- in effect, entering into a contract under false pretences. Both the church and the state decided that they had a substantial interest in the marital relations of citizens; the family was, after all, the basic unit of society and the source of citizens for the state and souls for the church. Accusations of impotence against a husband might also be introduced not by a wife but by relatives who might become heirs if a marriage were declared null. So the authorities became more and more involved in investigating the potency of men who had troubled marriages or greedy potential heirs.

The tests of potency were at best crude, culminating in an ordeal called "trial by congress" in which the man would try to prove his ability to make love by doing so in front of court-designated witnesses -- a circumstance that must have blunted the powers of more than one litigant. Many of the people involved in these trials were members of high society -- people well-known to the public, often with estates that made their ability to beget heirs a subject of considerable financial interest. There are almost no records of trials for impotency among the peasantry -- perhaps because they tended to be more robust people; more likely because nobody was very interested. But such trials among the nobility inspired considerable gossip and quite a few books -- court documents, personal accusations and vindications and reams of comic verse. Sides were taken and issues bitterly contested between those partisans who said the Marquis could and those who said he couldn't. In some cases, women even volunteered (humorously, of course) to help an attractive defendant prove his virility. In at least one case, where the man died before the case was settled, an autopsy was ordered, during which the ladies of the court laughed at the pitiful evidence of the deceased's physical imperfections.

Such case histories are undoubtedly the chief appeal of Darmon's book for the average reader, and one can find them (or fragments of them) in abundance. But the organization and scope of the book leave a lot to be desired for those with purely scholarly interests.