What is a fortiori argument?

A fortiori argument is a form of reasoning that draws a conclusion based on the assumption that if something is true in one case, it is even more likely to be true in a more significant or more compelling case. This type of argument emphasizes a comparison between two situations to assert that, if the first situation holds, the second situation must hold with even greater certainty or strength.

For instance, if someone argues that because a person can lift 50 pounds, it follows a fortiori that they can certainly lift 25 pounds, they are using the framework of a fortiori reasoning. The underlying logic is that if the more challenging assertion (lifting 50 pounds) is true, then the less challenging assertion (lifting 25 pounds) should also be true.

This method is useful in persuasive writing and arguments, as it builds upon established truths to strengthen assertions and create a compelling case for the position one is advocating. Understanding this form of reasoning allows debaters and advocates to effectively structure their arguments and appeal to logical reasoning in discussions.