Rational Self-Interest
As previously noted, the qualifier "rational" in the phrase "rational self-interest" is redundant. It is included here only for purposes of emphasis. Because one can determine what is truly good for one's life only by using one's reason, self-interest must necessarily be rational.

The determination of rational self-interest takes into account all relevant facts of reality. On the one hand, we must evaluate external factors—i. e., how one's actions impact one's relationship to physical reality and to other human beings. Yet we must not overlook internal factors—how one's actions impact one's mental functioning, including both thoughts and feelings. Because the mind is an integral part of the self, the impact of a person's actions on his or her mind cannot be ignored. Indeed, we have observed that the mind is a human being's most vital part, and the acting individual's psychological health is therefore of paramount importance.