The definitions of the terms we use have consequences for our ability to think and communicate clearly.
Imagine for a moment that your friend told you that he defines “carpenter” as “one who shapes wood by shooting it with a gun.” You’re baffled and you ask him what word he uses for someone who shapes wood by other means, such as a saw, lathe and sander. He says that he really has no word for this. He has a couple of synonyms for “carpenter,” but they also carry the implication that the person shaping the wood used a gun.
Hopefully, you can see that the problem with this hypothetical situation is not merely that you and your friend are using terms differently: shooting wood with a gun is a terribly impractical way of shaping it into useful forms. If the only concepts you have of wood shaping mean using a gun to do it, then you can’t really talk about those who shape wood using the practical methods in their profession.
Ayn Rand held that the common concept of “selfishness” is in an exactly analogous position to your hypothetical friend’s use of “carpenter.” At root, “selfishness” means pursuing one’s own interests and well-being. But the common use today adds in a second element: “pursuing your interests/well-being by means that are shortsighted and hurtful to others.” In today’s culture, the approximate synonyms of “selfishness,” such as “egoism” and “self-interest,” tend to be regarded with the same connotations of shortsightedness and harmfulness, so they are not much different.
Yet Ayn Rand rejected the idea that being shortsighted and hurtful to others is inherent in pursuing one’s interests and well-being. In fact, she recognized that the pursuit of one’s genuine interests in everyday life is specifically the opposite of “shortsighted and hurtful to others.” An individual’s genuine interests require long-term planning to fulfill, and his well-being is not served by doing harm to others. Attempting to pursue one’s self-interest by shortsighted and hurtful means is like trying to shape wood into a beautiful chair by shooting it with a pistol: utterly doomed to failure.