Base120 · Inversion

Contrapositive Reasoning

IN · Inversion

Use logical equivalence that if A then B equals if not B then not A

Model code
IN8
Transformation
IN (Inversion) — Improve by removing, reversing, or stress-testing assumptions.
Priority
8 of 20
Framework
HUMMBL Base120 — 120 mental models across 6 transformations

When to use

"Use when a conditional statement (if A then B) is hard to evaluate directly but the contrapositive (if not B then not A) is easier. The two are logically equivalent, so evidence against the contrapositive is evidence against the original."

Example

"If this feature is valuable, users will use it. Users do not use it (not B). Therefore the feature is not valuable (not A). This is logically valid — the question becomes whether the premise (if valuable then used) is actually true."

Common misuse

"Confusing the contrapositive with the converse. The converse (if B then A) is NOT equivalent to the original. If users use it, it is valuable does not follow from if it is valuable, users will use it."

Also known as

Contrapositive LogicModus Tollens

Related models

IN6IN4DE4