This mini-paper is to study how people of different moral standard choose their one-night-stand partners. At a late stage of this paper, I will state the limitations of this theory.

Assumptions: 1. Beauty and moral standard can be quantified. 2. People are utility-maximizing.

Almost all actions involve costs, needless to say having one-night stands. People of differnet backgrounds have different moral standards. For example, christians may have higher moral standards than people who left school very early do.

A person does an one-night-stand at a cost of his moral standard. For example, if the moral standard of a person offers him 5 utility, his one-night-stand partner must at least offer him more than 5 utility. Otherwise, he will not do this one-night-stand.

Generally, beauty and appearance produce utility. A beautiful partner offers higher utility than a ugly one does.

Let's see a case in which there are two people. The first one left school very early and had quite many experiences in sexual intercourse. The second one is a christian and has no such experience. The moral standards of the latter one is higher than that of the former one.

Ma = the moral standard of the former one = 3u Mb = the moral standard of the latter one = 6u

To have the former person to do an one-night-stand, his one-night-stand partner must at least offer him utility more than 3, while to have the latter person to do so, his partner mist at least offer him utility higher than 6.

Therefore, the one-night-stand partners of people who have higher moral standards have to be more beautiful than that of people who have lower moral standards.

How do we put this theory in test? It is very difficult. Unless we can have a common standard for beauty and moral standard, we are not able to test it.