It has only been over the last 180 years that sex has taken on some of its more prudish trappings, especially in America. With the advent of the reign of Queen Victoria of England in 1837, the western world adopted a much stricter and often oppressive view of sex that had far-reaching effects even into the 21st century. And although sexual standards today have loosened considerably since the Victorian era, there is still an element of prudishness that exists along with a curious double standard. In America, we allow our movie stars and entertainment celebrities all kinds of sexual licenses and liberties while holding our government officials, clergy, and common folk to stricter standards, often rooted in religious restrictions and taboos. Nudity, fornication, homosexuality, prostitution, pornography, and graphic depictions of sex in film and literature abound, but if we live these things out in our everyday lives, we are judged and condemned by our society as being of "loose moral character".
In 18th century Europe, there also existed a double standard, but not in the way that it exists today in the United States. The standards and regulations for men were much looser than those for women, and although some men were condemned by society as "libertines" (such as Casanova, who indulged in sexual relationships with the wives and daughters of noblemen), most men, especially those of the noble and higher educated working classes enjoyed their mistresses, and even relations with prostitutes, with little or no condemnation as long as they kept these relationships discrete. In the 18th century, medical science taught that a man needed regular sexual release and that without it, he would become ill. So in the event that his wife was pregnant and/or lactating, he would seek his sexual release in the bed of a mistress or prostitute. A mistress was much safer, and since she generally reserved herself for one man at a time, she was considered relatively free from venereal disease, whereas there was no telling who the prostitute had slept with and how many times. The sin of adultery for a man was not in his finding himself in the beds of other women, but in finding himself in love with a woman other than his wife, for the transfer of his affections to the other woman threatened the well-being of his wife and, most importantly, his legitimate offspring.
Women were limited to two sexual roles in 18th century western society--that of wife and mother, or mistress and/or prostitute. All women, no matter their station, were the property of men and were to be used in whatever way men saw fit. The virgin daughters of royalty and nobility were expected to keep themselves pure for their future husbands, and often in an effort to keep them chaste until marriage, they were sent off to convents at very young ages and schooled by nuns until they began to menstruate. Once their periods began, usually around thirteen to fourteen years of age, they were betrothed and married off, generally to much older men of noble blood. The wife of a nobleman was expected to be sexually faithful to her husband, for she was the vessel from which sprang his heirs. The only way to guarantee that his legitimate heirs would carry on his name and entitlements was in seeing to it that his wife engaged only in sexual relations with him. Her celibacy was paramount, while his celibacy was a personal choice and not required.
The mistress held a less respected, but generally well-loved and vital role in society, for it was the mistress who gave the man pleasure and release from the tensions at home. Mistresses were "kept" by their men, and therefore only noblemen or wealthy businessmen or members of the upper educated working classes could afford to keep them. It was in the bed of the mistress that the man could indulge his sexual fantasies, for sex with a mistress had nothing to do with procreation and everything to do with pleasure. The only sin that a man ever committed with his mistress happened when he fell in love with her. Because the church was loathe to grant divorces, abandonment was often the lot of the wife whose husband transferred his affections to his mistress, and the man who did so was usually blackballed by members of his class and society, making it nearly impossible for him to maintain himself financially. History is rife with stories of noblemen who fell in love with their mistresses--Lord Admiral Nelson with Emma Hamilton, Thomas Jefferson with Sally Hemings, and George IV with Maria Fitzherbert--but few, if any, ultimately abandoned their wives and children and/or titles and positions in order to marry their mistresses. Ultimately the mistress was abandoned whether it be by pressure from society or by the man's death, and in these cases, the mistress was generally left shattered, both emotionally and financially.
It is very clear, then, that the institution of marriage was created to benefit men in western society. Over the course of the last two-hundred years, however, especially with the advent of Women's Suffrage, and later the Women's Liberation Movement, women have made significant gains both sexually and within the institution of marriage. With these new freedoms have come changes in our views of sex and marriage and their roles and purposes within our society that have brought a great deal of conflict and confusion. Now sex is viewed more openly and is less about procreation as for pleasure and expression, and marriage as an institution is about two people who love each other and have decided to join their lives, industry, and property together in order to better care-for and support one another. There are still those pockets of our society that wish to hold on to the old norms and traditions, but overall the changes have taken hold and the result is a much different structure and view of not only sex, but human relationships in general, than what was prominent with our 18th century forefathers.