A horse walks into a bar.
The bartender says, "You're in here a lot. Are you an alcoholic?"
The horse ponders for a minute, then says, "I don't think I am." Then Poof! He disappears.
This is where Philosophy students start to snicker, since they are familiar with Descartes' postulate "I think, therefore I am."
...I could have told you that first, but that would have been putting Descartes before the horse.