Reading technique · Advanced
Contrapositive Reading
Reading a conditional clue backwards: if the consequence is false, the trigger must be false too.
Why it works
'If A then B' and 'if not B then not A' are the same statement. Most readers only watch for the trigger to fire; the backwards reading often resolves first.
Trigger
Any conditional clue, checked every time its consequence is ruled out rather than confirmed.
Common mistake
Only checking a conditional clue's forward direction, and never revisiting it when the consequence — not the trigger — becomes false.
Example
'If Mina is the baker, Theo owns the turtle' also means: if Theo doesn't own the turtle, Mina isn't the baker.
On Bambleweeny's board
Bambleweeny applies this automatically at Proficient and Expert difficulty. At Beginner difficulty it does not — one of the few places a careful reader can outperform the built-in solve.