I sure hope none of you ever used calculus.
People who think that ideas = property probably never had a bike stolen from them when they were a kid. If someone steals your bike, the thief has your bike and now you don't. If someone 'steals' your idea, congratulations! The thief has your idea, and now you still do. 'Theft' of ideas makes the world a better place for everyone. Especially if they are good ideas!