This is the classic “Dreadsbury Mansion” murder-mystery puzzle (problem #55 in Pelletier’s 1986 collection of automated-theorem-proving test problems), proposed by Len Schubert.
Someone in Dreadsbury Mansion killed Aunt Agatha. Agatha, the butler, and Charles live there, and are the only ones who do. Given:
- A killer always hates, and is never richer than, their victim.
- Charles hates no one that Agatha hates.
- Agatha hates everyone except the butler.
- The butler hates everyone who is not richer than Agatha.
- The butler hates everyone Agatha hates.
- No one hates everyone.
Who killed Agatha?
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