You shouldn't use someone's things without their permission.
George's roommates bought a new Playstation and is away at work.
George wants to play on the playstation.
George buys his own Playstation and plays it.
George decides to play on the Playstation while his roommate is at work.
When George's roommate finds out he is very excited, and they are able to play the same games together strengthening their friendship.
George's roommate gets very upset that he didn't ask for permission and decides to kick him out.