Final answer:
The correct claim for a psychological egoist is the fourth one, asserting that everyone always acts in their own self-interest. Psychological egoism suggests every action is motivated by self-gain, while objections note that people can act against their interests for other reasons.
Step-by-step explanation:
The claim of a psychological egoist aligns most closely with statement 4: "Everyone always acts so as to serve their own interests." Psychological egoism is the view that humans are always motivated by self-interest, and even acts of apparent altruism are done because of the personal benefits one expects to receive, either directly or indirectly.a
The argument for psychological egoism is that all human behavior can be explained by desires that aim to achieve what is perceived as one's greatest good. However, there are objections to this view, as it often confuses egoistic desires with motivation. For instance, an agent may act contrary to his desires if doing so serves a purpose that is not in his immediate self-interest, such as donating to charity over purchasing personal goods.
Additionally, the concept of ethical egoism, particularly strong ethical egoism, posits that it is always right to aim at one's own greatest good. This aligns with rational egoism, which suggests it is always rational to do so. However, there are objections that highlight situations where solely pursuing one's self-interest may not lead to the good of others, and may result in conflicts, suggesting the need for a balance and sometimes acting against one's narrow self-interest.