So a horse walks into a bar... So a horse walks into a bar. The barkeep seems to know that the horse frequently goes to bars, and he asks the horse, ""Aren't you an alcoholic by now?"" The horse replies, ""I think not!"" and disappears, seemingly into thin air. See, the joke here is based on Rene Descartes' famous philosophy of ""I think, therefore I am"", however, explaining that part first would be putting Descartes before the horse.