In every case, laughter results from nothing but the suddenly perceived incongruity between a concept and the real object that had been thought through it in some relation; and laughter itself is just the expression of this incongruity…All laughter therefore is occasioned by a paradoxical, and hence unexpected, subsumption, it matters not whether this is expressed in words or deeds.
…the origin of the ludicrous is always paradoxical, and thus unexpected, subsumation of an object under a concept that is in all other respects heterogeneous to it. Accordingly, the phenomenon of laughter always signifies the sudden apprehension of an incongruity between such a concept and the real object thought through it, and hence between what is abstract and what is perceptive. The greater and more unexpected this incongruity in the apprehension of the person laughing, the more violent will be the laughter. '
Arthur Schopenhauer- The World as Will and Representation.