Al memo No. 603, November, 1980, published in Minsky, Marvin, "Jokes and their Relation to the Cognitive Unconscious," Cognitive Constraints on Communication, Vaina and Hintikka (eds.) Reidel, 1981. This version of the paper may have misprints because it is a prepublication draft. JOKES and the Logic of the Cognitive Unconscious Marvin Minsky, MIT Abstract: Freud's theory of jokes explains how they overcome the mental "censors" that make it hard for us to think "forbidden" thoughts. But his theory did not work so well for humorous nonsense as for other comical subjects. In this essay I argue that the different forms of humor can be seen as much more similar, once we recognize the importance of knowledge about knowledge and, particularly, aspects of thinking concerned with recognizing and suppressing bugs—ineffective or destructive thought processes. When seen in this light, much humor that at first seems pointless, or mysterious, becomes more understandable. Introduction A gentleman entered a pastry-cook's shop and ordered a cake; but he soon brought it back and asked for a glass of liqueur instead. He drank it and began to leave without having paid. The proprietor detained him. "You've not paid for the liqueur." "But 1 gave you the cake in exchange for it." "You didn't pay for that either" "But 1 hadn't eaten it". —Freud (1905). In trying to classify humorous phenomena, Sigmund Freud asks whether this should be called a joke, 'for the fact is we do not yet know in what the characteristic of being a joke resides." Let us agree that some of the cake-joke's humor is related to a logical absurdity—leaving aside whether it is in the logic itself, or in keeping track of it. Later Freud goes on to ask what is the status of a "knife without a blade which has no handle?" This absurdity has a different quality; some representation is being misused—like a frame without a picture. Freud, who never returned to the subject after writing his 1905 book on t