Charlie Chaplin is popularly credited with this line, though, like most quotable people, he probably said something close to it in more than one place, and the version we have is the smoothest survivor. Chaplin had built an entire career on the economic value of laughter at a time when millions of people had nothing else that was working. He was not sentimental about it. He treated laughter as infrastructure.

The sentence looks like motivational decoration and is not. Chaplin grew up in a London workhouse, watched his mother committed to an asylum, and spent the First World War turning grief into slapstick for audiences who had nothing to spend except an hour. He knew, precisely, what a day without laughter cost. The body stiffens. The mind contracts. The small openings through which the next good thing could enter narrow. A day can be survived without laughter. It can rarely be inhabited.

A cat caught mid-sneeze, eyes crossed, ears back, face briefly entirely un-dignified, is a guaranteed laugh for whoever saw it. The cat did not mean to be funny. The cat is probably mildly annoyed. That is the whole comedy. Laughter is rarely produced on command. It is nearly always a by-product of something ordinary going slightly wrong in the presence of witnesses. Chaplin built a fortune on exactly that. The sneezing cat, Instagram aside, works for free.