Contrapositives — Your Most Powerful Tool

Every conditional has a contrapositive. Always write it.

Original: If A → B

Contrapositive: If not B → not A

Chain example:

If A → B. If B → C. Chain: If A → B → C.

Contrapositive of chain: If not C → not B → not A.

Logic Games application:

Rule: "If Sarah is selected, Tom is also selected." S → T

Contrapositive: not T → not S. If Tom is OUT, Sarah is OUT.

LR application:

"All successful businesses innovate." Success → Innovation.

Contrapositive: No innovation → No success.

INVALID: Innovation → Success (affirming the consequent).

Drill: Write the contrapositive of every conditional you encounter. Make it automatic.

Reference:

Wikipedia: Contraposition

https://en.wikipedia.org/wiki/Contraposition