Psychological egoism is known as a descriptive theory regarding the only end of human activity to be self-interest. This paper has tried to study the proofs of the theory critically. At first, the role of reason and feelings in forming human will have been explained. To do so, Hume and Kant’s views have been reconsidered and, finally, that of Hume with a partial addition has been preferred. It should be stated that the main proofs of egoism are essentially philosophical, and, therefore, one may not oppose them by experience. Altruism, on the contrary, views human motivations to be numerous and argues against egoist overall motivations. In this way, the claim of psychological altruism, contrary to egoism, is limited, and, therefore, it can be proved with some small cases of altruist fundamental acts or tendencies. Psychological egoists have presented four proofs for the theory, some include fallacy and others are incomplete. Finally, it can be said that the theory is baseless, and, therefore, the most important proof of ethical egoism is in vain.