I am asking this question on behalf of one of my agnostic friends. My friend believes that having sex before the marriage is not a big issue. She thinks that it is actually healthy to have sex before marriage as it helps you understand the other person not only emotionally but also physically. At the same time, according to her, it does not impact the family system, as we cannot say that in a society where the sex is prevalent has more divorces than the one without it. She thinks that sex is a natural need of human beings and since nowadays marriages are late, there is no harm if a person has sex before marriage. Can you please help me make her understand why it is not good for society, that person and the institution of family to allow sex before marriage? I will be grateful for your answer.
I think It is too simplistic if we consider the two factors of 'divorce rate' and 'knowing the person better' as the only important factors and then without any reliance on any statistics about these factors decide whether something is good or not.
Arguments can be made for both sides. With the lack of proper statistics it is impossible to come up with any conclusions about the actual effects of sex or no sex before marriage in societies.
One thing I can say, not based on any scientific study but based on my own observation (as some one who has lived in both kinds of societies with regard to allowance or forbiddance of sex before marriage) is that I have seen that while the concept of family is still a relevant concept in societies where sex before marriage is not allowed, the concept is becoming less relevant as times passes, in societies where this is allowed. I have seen that the very fact that people can have sex before marriage has contributed in being less interested in forming a family.
Also, I have seen that in societies where sex before marriage is allowed, thirst for new and not normal ways of sex is much higher than in societies where sex before marriage is not allowed. In other words, it seems to me that in the societies where sex before marriage is not allowed, most people feel sexually satisfied when they will be able to have sex with their spouse. However where, as the result of allowance of sex before marriage, sex is quite common and accessible in the society, it seems to me that having sex with the spouse is not at all satisfying for many and they look for new frontiers in sexual experience.
Also bear in mind that in reality, in societies where sex before marriage is allowed, people are not doing this in order to know their possible future spouse better from physical point of view. Many do this just for pleasure. We should not ignore the vital effect of this on the society. Overall, I have found the societies in which sex before marriage is allowed much less moderate than the ones that forbid this. In fact, while the concept of 'Hayaa' is a very crucial concept among the communities where sex before marriage is not allowed, I have not seen much of this concept in societies where sex before marriage is available. In fact, the English word 'modesty' does not seem to carry the concept of 'Haya' anymore and I am not aware of any other English word for this concept!
I emphasize again that the above is purely based on my personal observation and is not based on any stats.
However, to answer your friend, I think we are approaching the problem from the wrong end.
Does your friend believe in God? You said she was agnostic so that means she is not sure.
Does she believe that human beings know perfectly what is best for them?
If the answer to the first question is No or Not Sure, or if the answer to the second question is Yes, then, given the lack of any definite statistics for or against sex before marriage, I suggest you discuss these two questions with her as well.
Once one agrees that there is God and that human beings do not have a perfect understanding of what is best for them, then it will be only natural to expect God to let us know what is best for us. All the Abrahamic religious and most of the non-Abrahamic religions advise against sex before marriage. I think there is a clear message there for some one who believes in God and believes that human beings need guidance.