Why do jokes make us laugh? The human mind rejoices when it perceives a great truth. Religious ecstasy and the eureka of scientists are instances of this. For true religious experience is the recognition of a profound truth about the essence of our being, and a scientific discovery is the unveiling of a profound truth about the world around us. The human mind is amused when it recognizes a small truth.
The laughter at a joke is an expression of that amusement, for ultimately every (good) joke exposes some little truth or other about humanity, inanimate nature, ideas, words, or whatever. Laughter is an expression of mild ecstasy.
If great truths are like the nutritional essence of what we eat, small truths are like the sweeteners and spices that enhance the taste of the food.
Likewise, if religion and science raise us to lofty heights, jokes and humor add spice to living.