a-monster
Explanation
The Joke
A child tells their parents there is a monster in the dark. The father, rather than comforting the child, launches into a pedantic epistemological argument: he explains that it is impossible to know what happens in pure darkness, because in order to verify there is no monster you would need to see, but seeing requires light, and light would eliminate the darkness. He essentially argues that you cannot disprove the existence of a monster in the dark because observation requires illumination. The mother, unimpressed by this philosophical tangent, tells him to comfort the child. The father warns against it -- "They can smell fear" -- and the final panel shows him fleeing, yelling "Come on!"
The Humor
The comedy comes from the father treating a child's simple fear as a legitimate epistemological puzzle rather than just offering reassurance. His argument is technically sound in a trivially pedantic way -- you truly cannot visually confirm what is in complete darkness without adding light -- but it is absurdly unhelpful as parenting. The twist at the end reveals he has actually scared himself with his own reasoning: having convinced himself that a monster in the dark is unfalsifiable, he now genuinely believes it could be there. The line "they can smell fear" confirms he has gone from philosophical skeptic to full-on believer, and he panics more than the child does.