A dinner party guest list that only makes sense with one guest
A man wants to host 'a very small dinner party' and invites his father's brother-in-law, his brother's father-in-law, his father-in-law's brother, and his brother-in-law's father. What is the smallest number of guests he could actually be inviting?
Reveal the answer
One. All four descriptions can refer to the very same single man, depending on how the family is arranged — Lewis Carroll built the riddle to show how relationship puzzles can collapse multiple-sounding descriptions into one person. It appears in 'Eligible Apartments,' the second of the ten mathematical stories making up A Tangled Tale (1885).
— Lewis Carroll, A Tangled Tale — Knot II: Eligible Apartments, 1885
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