# Modus ponens

**Modus ponens** (Latin: *mode that affirms*) is a valid, simple argument form:

- If P, then Q.
- P.
- Therefore, Q.

The argument form has two premises. The first premise is the "if-then" or *conditional* claim, namely that P implies Q. The second premise is that P, the *antecedent* of the conditional claim, is true. From these two premises it can be logically concluded that Q, the *consequent* of the conditional claim, must be true as well.

Here is an example of an argument that fits the form *modus* *ponens*:

- If democracy is the best system of government, then everyone should vote.
- Democracy is the best system of government.
- Therefore, everyone should vote.

For an amusing dialog that problematizes modus ponens, see Lewis Carroll's "What the Tortoise Said to Achilles."

See also: modus tollens, affirming the consequent, Denying the antecedent, inference rule.