One should be selfish because a person should only live one's life as an individual, and one should only take actions and make decisions by using one's natural ability to think sensible . Therefore, people must only act according to their own individual interests, not those of others , as their interests are what will benefit their own lives. However, these interests must be based on principles derived from the reason of their own minds, which is founded on their intelligence, growth, and understanding of reality. This is based on the idea that every human possesses the natural right to her own life, and this idea extends to social existence.
Even when a person lives in a society which is favourable for human survival, his purpose for living should still be for himself / herself and not for others. The theory refute social ethical theories such as communism, which decree that a person's purpose for living is to benefit the lives of all people. Her theory also rebut religious ethical theories, which decree that a person's purpose for living is for a supreme being—one god or many gods—depending on which religion he / she belong to.
Good start. I would like you to elaborate more on your understanding of selfishness. Define it and give examples of what is truly in your rational self-interest.
I will give you a 25% upvote. Hope to see more in depth content from you where you go more deep into the ideas.
Ok bro