In a bar, a well-drunk patron insists that the boss serve him a last gin.
"Come on, Jack! Give me another drink. You see I'm not so drunk."
The bartender replies "You're kidding, you're just standing on your legs. "
"No, Jack! You want a proof? Well, look at the dog coming into your bar. From here, I can tell you that he only has one eye. You see, I'm ok."
The bartender laughs and says "Ah yes! I see. But you know that the dog in question isn't coming into the bar, it is leaving!"