Suppose that some one tells the following story: An Indian at an Englishman's table in Surat saw a bottle of ale opened, and all the beer turned into froth and flowing out.The repeated exclamations of the Indian showed his great astonishment."Well, what is so wonderful in that?" asked the Englishman."Oh, I'm not surprised myself," said the Indian, "at its getting out, but at how you ever managed to get it all in." At this we laugh, and it gives us hearty pleasure.This is not because we think ourselves, maybe, more quick-witted than this ignorant Indian, or because our understanding here brings to our notice any other ground of delight.It is rather that the bubble of our expectation was extended to the full and suddenly went off into nothing.Or, again, take the case of the heir of a wealthy relative being minded to make preparations for having the funeral obsequies on a most imposing scale, but complaining that things would not go right for him, because (as he said) "the more money I give my mourners to look sad, the more pleased they look."At this we laugh outright, and the reason lies in the fact that we had an expectation which is suddenly reduced to nothing.We must be careful to observe that the reduction is not one into the positive contrary of an expected object-for that is always something, and may frequently pain us-but must be a reduction to nothing.For where a person arouses great expectation by recounting some tale, and at the close its untruth becomes at once apparent to us, we are displeased at it.So it is, for instance, with the tale of people whose hair from excess of grief is said to have turned white in a single night.On the other hand, if a wag, wishing to cap the story, tells with the utmost circumstantiality of a merchant's grief, who, on his return journey from India to Europe with all his wealth in merchandise, was obliged by stress of storm to throw everything overboard, and grieved to such an extent that in the selfsame night his wig turned grey, we laugh and enjoy the tale.This is because we keep for a time playing on our own mistake about an object otherwise indifferent to us, or rather on the idea we ourselves were following out, and, beating it to and fro, just as if it were a ball eluding our grasp, when all we intend to do is just to get it into our hands and hold it tight.Here our.gratification is.not excited by a knave or a fool getting a rebuff: for, even on its own account, the latter tale told with an air of seriousness would of itself be enough to set a whole table into roars of laughter; and the other matter would ordinarily not be worth a moment's thought.
It is observable that in all such cases the joke must have something in it capable of momentarily deceiving us.Hence, when the semblance vanishes into nothing, the mind looks back in order to try it over again, and thus by a rapidly succeeding tension and relaxation it is jerked to and fro and put in oscillation.As the snapping of what was, as it were, tightening up the string takes place suddenly (not by a gradual loosening), the oscillation must bring about a mental movement and a sympathetic internal movement of the body.This continues involuntarily and produces fatigue, but in so doing it also affords recreation (the effects of a motion conducive to health).