Second-hander:A person who looks to others to decide his values or beliefs.
The term comes from The Fountainhead. It describes people who don't deal with reality directly, but instead look to others. Instead of trying to understand the world, they simply accept what other people tell them, without attempting to evaluate that information. Instead of trying to decide what values would benefit their lives, they look to others and trust that they must be right.
A second-hander does not think for himself. He does not even act for himself. He lives in order to impress others. It doesn't matter if he's happy if he can trick others into believing he's happy. It doesn't matter if he's wealthy, if he can trick others into believing he's wealthy. The only thing that matters is what other people thing or believe.
In practice, people mix a little second-handedness into their lives. They look to impress others by acquiring things that others would want. They profess to believe things they don't really accept in order to fit in. They ignore their own judgments or evaluations when they conflict with other people's. They sacrifice their own values for the sake of fitting in.