Modus ponens

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Modus ponens is a valid, simple argument form:

If P, then Q.
Therefore, Q.

Basically the idea is to make an "if-then" claim--these are called conditional claims--and then affirm the "if" part, or the antecedent, and then conclude with the "then" part, or the consequent.

In symbols:

 A → B
 ∴ B

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.

See also: modus tollens.