The terms "self-interest" and "selfishness" are often considered equivalent. In fact, at least one dictionary bases one of its definitions of "selfish" on "self-interest." Unfortunately, there are two distinct concepts that are often confused. To make a distinction between the two concepts, I use the two words differently. When I use "self-interest" I mean what someone thinks is best for themselves. When I use "selfishness" I mean putting your one’s own desires first at the expense of others (especially those who have an equal or greater claim).

Here is an illustration. A child who plays with his own toys during playtime by himself is not being selfish, but a child who demands the toys other children are playing with during a play date is being selfish.

I believe everyone always acts in self-interest. How it fits self-interest is not always immediately obvious. People do nice things for others because it garners respect, because it feels good, because they think it will benefit them by creating the kind of culture they want to live in, because they think it will be rewarded after death, or for other reasons that they think make it best for them even if they expect it to cause some other loss to themselves (for example giving away money causes a financial loss). This doesn’t mean that people are always thinking about themselves. It doesn’t mean that whenever they make a decision they only think about themselves. It just means that when people make a decision they always choose what they consider to be best for themselves (even in self-sacrifice). People may not even know all the factors in their decision. For example- they may have a fear that they aren’t thinking of, but convinces them not to do something they may intellectually agree is good for them.

Self-interest is not wrong or bad. If it were bad, why would it be used for motivation in the Bible? Jesus exhorts people to "lay up for yourselves treasures in heaven" (Matthew 6:20). The beatitudes start with "blessed." Why would Jesus tell them how to be "blessed" if seeking after something good for yourself (like blessing) is bad?

It is assumed in other instruction. In telling people to "love your neighbor as yourself" (Matthew 22:39), the assumption is that people do love themselves. If you don’t love yourself than telling you to love your neighbor as yourself is not telling you to love your neighbor at all. In Ephesians, Paul says "husbands should love their wives as their own bodies" (Ephesians 5:28). This again assumes that they already love their own bodies. That same verse goes on to say "He who loves his wife loves himself."

Jesus even acted in his own self-interest. Hebrews 12:2 says that Jesus "for the joy that was set before him endured the cross." Did you catch that? He endured the cross for joy. It doesn’t say he did it out of disinterested benevolence.