There is a kind of marriage called “open marriage.” It refers to a marriage in which the partners agree that each may engage in extramarital sexual relationships, without this being regarded as infidelity. In an open marriage, the partners have no promise to keep the loyalty of sex. So, in this way, they will not break the promise because there is even no one. And certainly, we cannot regard this kind of adultery as immoral.
What’s more, even though there is a promise for the loyalty of sex in some marriage, when adultery happens, we still cannot directly call it immoral. For example, there is man who had a car accident and has been paralyzed. He was too afraid to lose his wife, so he strongly required her loyalty of sex. When time flies, his wife has spared no efforts to take care of the other for years, she finally committed adultery because her spouse couldn't satisfy her sexual needs. In this case, should we call it immoral? The wife has done what she should and could do. However, she is just like all of us, being a human and has physical needs. She deserves a better life, and adultery just a way she used to pursue her own happiness.
In general speaking, hostility toward adultery is seen as a useful way to protect marriage. But, if it is really useful, then why is adultery widespread, and does divorce rate get higher and higher? So, it is still question that whether discrimination toward adultery can protect marriages. However, I have discussed in Annotation 1 that adultery can be an alternative way to save one’s marriage and also oneself from possible problems happening in the future. In conclusion, adultery deserves a different comment other than “immoral.” And even, we cannot ignore its positive effects. “Not every adultery is the same,” which means not every adultery is immoral!
Ying-Bin Ning (May, 2002). 通姦不道德嗎? 自由時報