The Contrapositive Explained: The Most Important LSAT Conditional Skill

If you want to score well on the LSAT, you must understand the contrapositive. It’s one of the most frequently tested logical tools, and once you fully internalize it, conditional reasoning becomes far more predictable — even easy.

What Is the Contrapositive?

A contrapositive is the logically equivalent version of a conditional statement.

To form it, you do two things:

1. Flip the order of the terms

2. Negate both sides

Example:

If you eat peanuts → you’ll have an allergic reaction.

The contrapositive is:

If you don’t have an allergic reaction → you didn’t eat peanuts.

Same truth value. Same meaning in logic. Perfectly interchangeable on the LSAT.

Why It Matters

The LSAT regularly hides the contrapositive inside:

• Must Be True questions

• Sufficient assumption questions

• Parallel reasoning

• Flaw questions

Students who don’t see contrapositives get stuck. Students who do? They move faster and score higher.