Adultery is defined to be sex with a person who is not your spouse. Note this definition implies that you must be married. An unmarried person cannot commit adultery. They can do something which is known as "cheating", but it will not be called adultery, to commint adultery on someone, you must be married to that person. The Biblical punishment for adultery is death. This practice can still be found in the uncivilized Islamic countries today. Adultery clearly has some problems with it. If the husband commits adultery on his wife, and his wife founds out about it, it can lead to a breakdown of his entire family, which is obviously a problem. However, there are certain conditions under which adultery would be acceptable and in fact may even be a good idea.
Part of the problem of many relationships is that the husband wants to be involved with other women. This is natural and in male nature. Evolution designed men to want to be polygamous and spread their sperm to as many women as they can. When a male marries a woman and stays with her he is fighting against his nature. This male nature is part of many relationship problems. I believe that if we accept this condition of men as normal and find ways to incorporate it into relationships in a reasonable manner then it can lead to stronger relationships between the husband and the wife.
What the wife needs to understand is that her husband, if he fantasizes about other women, or watches porn, does not necessarily no longer love her anymore. Just because he wants someone else's pussy does not mean he wants to run away with a different woman. Understand that his desire for other women is purely lust based, he does not want to live with them, just sleep with them. Likewise, just because a guy still masturbates in a relationship does not necessarily imply that he no longer wants his wife or her pussy. It just meant that he wanted a way to relieve himself.
By the reasoning above it follows that if a wife catches her husband taking out another woman other to dinner she should be more concerned than if she catches him in bed with another woman. Because if she catches him in bed then she can assume it was only lustful for him. But if she catches him having dinner with another woman then she should be concerned that perhaps he wants to leave her with another woman.
The kind of adultery that would be justified is the kind in which the wife is fully aware of what her husband is doing. The husband would tell her that he has a temptation to sleep with another woman and his wife would understand. His wife would understand that for him sex with a different woman is just like masturbation for him. Just done out of lust. In that way the husband would be able to relieve himself with a different woman and still maintain a strong relationship with his wife.
The problem is when the wife refuses to accept this polygamous male nature. Then the husband knows that he cannot tell his desires to his wife. Because if he told his wife his desires of other women then she would get very angry and it may lead to an end of a relationship (just shows you how "love" is not so much about actual love, but I am getting off topic). But if his wife was open-minded and understood his dilemma, and furthermore did not stop him from engaging other women then his problem would be relieved and their relationship would stay the same. But in our current modern value system adultery is treated as always wrong, and so the husband must hide this from his wife. Which very often leads to a complete breakdown of the marriage.
Strong relationships are based on honesty and being open with the spouse. The desire to have sex with others is just another issue that should be explored between couples if they wish to maintain a strong relationship. I hope that the future of humanity will change their perception of adultery to allow for the scenario that I described. It should lead to improved marriage. And it is in this way that adultery can be an aid to protect marriages, not to destroy them.
I should be a marriage counselor, I have some strange ideas for couples.