Léon Dumont (February 5, 1837, Valenciennes - January 17, 1877, Valenciennes) was a French psychologist and philosopher. He influenced Nietzsche and William James and is perhaps best known for his treatise on the causes of laughter (Des causes du rire).
Dumont's closing thoughts from the last page of Des causes du rire
The miserable beggar said to the King of France, "Thy image is everywhere except in my pocket." One has seen that to laugh is to disarm hate and anger and to extract from some judges indulgence for a sin. In a word, the good joke, applied appropriately to any subject, has the effect of sweetening the deal for us: Ridiculum acri fortius et melius magnus plerumque secat res. - Horace (A good joke often cuts an important deal strongly and sweetly.) But, like any free action, the joke submits to the law of morality; the joke is virtuous or the joke is evil. In general, the joke only has moral value in the mouth of a morally serious person.