Consider one of those features of people that set them apart from other species: laughter. No other animal laughs. What we call the laughter of the hyena is a species sound that happens to resemble human laughter. To be real laughter it would have to be an expression of amusement—laughter at something, founded in a complex pattern of thought. True, there is also "laughter at what ceases to amuse," as Eliot puts it. But we understand this "hollow" laughter as a deviation from the central case, which is the case of amusement. But what is amusement? No philosopher, it seems to me, has ever quite put a finger on it. Hobbes's description of laughter as "sudden glory" has a certain magical quality; but "glory" suggests that all laughter is a form of triumph, which is surely far from the truth. Schopenhauer, Berson, and Freud have attempted to identify the particular thought that lies at the heart of laughter: none, I think, with more than partial success. Helmuth Plessner has seen laughing and crying as keys to the human condition, features that typify our distinctiveness. But his phenomenological language is opaque and leads to no clear analysis of either laughter or tears,
One contention, however, might reasonably be advanced, which is that laughter expresses an ability to accept our all-too-human inadequacies: by laughing we may attract the community of sentiment that inoculates us against despair. . . . From that suggestion, however, another follows. Only a being who makes judgments can laugh. Typically we laugh at things that fall short or at witticisms that place our actions side by side with the aspirations that they ridicule.
-Roger Scruton, On Human Nature