The social contract theory of morality claims that no eternal principles are required in order for m

* This is not 250 words, but it should give you a sense what's being asked.

According to the social contract theory, an act is morally right only if it is permitted by social contract for the society of its agents at the time it is performed. In other words, what we consider to be moral today, isn't necessarily guarenteed to be moral tomorrow; thus, no eternal principles exists. As long as society uploads the necessary laws and moral rules for social living, such as prohibitions on lying, murder, and theft, that in itself is mutually beneficial for all. Of course, on the condition that it is reciprocated by all others that follow the rules. When reciprocity violated, however, you are permitted to break the rules/laws -- again, morality is not eternal. For example, the civil disobedience during the civil rights movement can be seen as legitimate and reasonable response to a violation of the social contract. In order to gain the benefits of social living, we must accept the burdens of social living (obeying the laws), but again, these laws are subject to change contingent on reciprocity and other moral grounds.