Humour resides in the perception of limitation, in discerning how often the conventional principle is belied by the actual practice.  The old world was full of a youthful sense of its own importance; it held that all things were created for man—­that the flower was designed to yield him colour and fragrance, that the beast of the earth was made to give him food and sport.  This philosophy was summed up in the phrase that man was the measure of all things; but now we have learnt that man is but the most elaborate of created organisms, and that just as there was a time when man did not exist, so there may be a time to come when beings infinitely more elaborate may look back to man as we look back to trilobites—­those strange creatures, like huge wood-lice, that were in their day the glory and crown of creation.  Perhaps our dreams of supremacy and finality may be in reality the absurdest things in the world for their pomposity and pretentiousness.  Who can say?

But to retrace our steps awhile.  It seems that the essence of humour is a certain perception of incongruity.  Let us take a single instance.  There is a story of a drunken man who was observed to feel his way several times all round the railings of a London square, with the intention apparently of finding some way of getting in.  At last he sat down, covered his face with his hands, and burst into tears, saying, with deep pathos, “I am shut in!” In a sense it was true:  if the rest of the world was his prison, and the garden of the square represented liberty, he was undoubtedly incarcerated.  Or, again, take the story of the Scotchman returning from a convivial occasion, who had jumped carefully over the shadows of the lamp-posts, but on coming to the shadow of the church-tower, ruefully took off his boots and stockings, and turned his trousers up, saying, “I’ll ha’e to wade.”  The reason why the stories of drunken persons are often so indescribably humorous, though, no doubt, highly deplorable in a Christian country, is that the victim loses all sense of probability and proportion, and laments unduly over an altogether imaginary difficulty.  The appreciation of such situations is in reality the same as the common and barbarous form of humour, of which we have already spoken, which consists in being amused at the disasters which befall others.  The stage that is but slightly removed from the lowest stage is the theory of practical jokes, the humour of which is the pleasure of observing the actions of a person in a disagreeable predicament which is not so serious as the victim supposes.  And thus we get to the region illustrated by the two stories I have told, where the humour lies in the observation of one in a predicament that appears to be of a tragic character, when the tragic element is purely imaginary.  And so we pass into the region of intellectual humour, which may be roughly illustrated by such sayings as that of George Sand that nothing is such a restorative as rhetoric, or the claim advanced by a patriot that