چراغ مرد نابینا

A blind man is walking along a road on a dark night. He carries a lamp in his hand and a jug on his shoulder. Another man questions the point of taking a light along. Since the blind man cannot see, he says, daylight and darkness must be the same to him. He calls the blind man's behaviour foolish.

The blind man laughs and explains that the lamp is for other people. Its light allows them to see him, avoid bumping into him and keep his jug from being broken. He does not need to see the light himself for it to be useful.

The answer turns the criticism back on the questioner. The person who seemed to be doing something pointless understands his situation better than the man who can see. The joke is complete with the explanation; the story does not describe a collision or a broken jug.