Why is egoism unique among ethical theories? It is the only theory to equate what is good to what is performed in the name of self-interest. It is the only theory to explain the way things ought to be in regards to what is right and wrong. It is the only theory to acknowledge conflicting interests as harmful to a system of ethics. It is the only theory to maintain that there are no universal truths regarding what is good.

I think what makes it unique is that it's alternative, altruism, is often debated to be near impossible. There are those who claim egoism is human nature and those who think that people are capable of any form of thought, thus allowing one to be truly altruistic. Many think that even when one is consciously doing something for others, they are subconsciously acting in self-interest.    

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is there a year set? the question is incomplete