- If P, then Q.
- Therefore, P.
Arguments of this form are invalid, in that arguments of this form do not always give good reason to establish their conclusions, even if their premises are true.
One way to demonstrate the invalidity of this argument form is with a counterexample with true premises but an obviously false conclusion. For example:
- If Bill Gates owns Fort Knox, then he is rich.
- Bill Gates is rich.
- Therefore, Bill Gates owns Fort Knox.
Arguments of the same form can sometimes seem superficially convincing, as in the following example: