Do you believe in the Devil?

Justice Scalia surprised the New York Magazine by saying that he believes that the Devil is real.  Do you believe that the Devil is real too?

Apparently the interviewer doesn't.  It seems that the interviewer was surprised that any learned people today would believe in the devil.  So Justice Scalia had to explain himself.

He has read the Screwtape Letters.  He has read the Bible.  He believe that the Devil is alive and deceptive and continues to try to trick people away from the ways of the true and righteous God.

What do you believe?  Is it folklore to believe in the Devil?  Is it superstition?  Is it a concept from the old days that we no longer need today?  Should the devil be confined to the horror genre of fiction, and not be treated seriously?

What about the Bible?  Should the Bible be treated as fiction too?

Why do you believe what you do?