In the system of free sexual relationships...
In the system of free sexual relationships, the marriage contract ends the free period of boys and girls and it obliges them to learn to be loyal to each other whereas in the Islamic system, their deprivation and anticipation is met.
The system of free relationships, in the first place, causes boys to become soldiers of fortune because of marriage and the formation of a family and not until their high, young spirits tend to become weak, they turn to marriage; then a girl is taken because she will bear children or clean the house or act as a maid. In the second place, it weakens the roots of the existing marriage.
Instead of the marriage being based upon a pure love and deep affection where they know their partner to be the person who shares in their happiness, the reverse happens. They look at their partner with the eyes of a competitor, as a person who prevents freedom and brings limitations. As they say, each one becomes the other's prison guard. When a boy or a girl wants to say, "I am married", but instead says, "I have taken on a prison guard". What does this mean?
This means that before marriage, they were free to go wherever they wanted to flirt; there was no one to tell them what to do. But after marriage, these freedoms were limited. If a man goes home late one night, there will be an argument with his partner. "Where were you?" If he talks with a young girl, his wife objects. It is clear to what extent family relations become weakened and cold in such a system.
Some people like Bertrand Russell believe that the prevention of free relationships is not just for the certainty of men in relationship to future generations because methods of birth control have been developed to solve this difficulty. Thus, the issue is not just the knowledge of who the father is. The other issue is that the purest of emotions exist between the marriage partners and the relationship should be based on unity and solidarity.
These goals can only be met when the partners close their eyes to other relationships, when the man closes his eyes to other women, when the wife is not bent on stimulating and attracting anyone but her husband and when the principle of forbidding the satisfaction of sexual desires outside of the family, even before marriage, exists.
In addition, when a woman who has progressed following Russell and people like him and in accordance with the 'new sexual ethics' still seeks her love in another in spite of having a legal husband.