The incongruity theory is the reigning theory of humor, since it seems to account for most cases of perceived funniness, which is partly because “incongruity” is something of an umbrella term. Most developments of the incongruity theory only try to list a necessary condition for humor—the perception of an incongruity—and they stop short of offering the sufficient conditions.
In the Rhetoric (III, 2), Aristotle presents the earliest glimmer of an incongruity theory of humor, finding that the best way to get an audience to laugh is to setup an expectation and deliver something “that gives a twist.”
After discussing the power of metaphors to produce a surprise in the hearer, Aristotle says that “[t]he effect is produced even by jokes depending upon changes of the letters of a word; this too is a surprise. You find this in verse as well as in prose. The word which comes is not what the hearer imagined.”
These remarks sound like a surprise theory of humor, similar to that later offered by René Descartes, but Aristotle continues to explain how the surprise must somehow “fit the facts,” or as we might put it today, the incongruity must be capable of a resolution.
In the Critique of Judgment, Immanuel Kant gives a clearer statement of the role of incongruity in humor:
“In everything that is to excite a lively laugh there must be something absurd (in which the understanding, therefore, can find no satisfaction).
Laughter is an affection arising from the sudden transformation of a strained expectation into nothing” (I, I, 54).
Arthur Schopenhauer offers a more specific version of the incongruity theory, arguing that humor arising from a failure of a concept to account for an object of thought. When the particular outstrips the general, we are faced with an incongruity. Schopenhauer also emphasizes the element of surprise, saying that “the greater and more unexpected [. . .] this incongruity is, the more violent will be his laughter” (1818, I, Sec. 13).As stated by Kant and Schopenhauer, the incongruity theory of humor specifies a necessary condition of the object of humor.
Focusing on the humorous object, leaves something out of the analysis of humor, since there are many kinds of things that are incongruous which do not produce amusement.
A more robust statement of the incongruity theory would need to include the pleasurable response one has to humorous objects.