acting in one's self-interest; generally referred to as selfishness. There are two forms. Ethical egoism: even though we can act in the interests of others, we should always act only in our own interests. Writer Ayn Rand promoted ethical egoism. Psychological egoism: that we cannot act in the interests of others, and anything that appears to be such is actually a selfish act, because we expect to personally benefit from it.