If I can’t beat my grandpa at basketball, then I can’t beat LeBron James. Fact.
We hear this kind of argument a lot. It can be humorous, poignant, often compelling. It’s a favorite of lawyers and children and a great set up for Horatio Caine jokes.
It’s called argument a fortiori (ah-four-tee-OR-ee) or “argument from the stronger.” And it can be hours of rhetorical fun.
The argument’s composition is easy. The content is where you get to show off your creativity.
A fortiori arguments require two related propositions:
- One is less probable.
- One is more probable.
Here’s where the magic happens: To whatever degree you can prove #1, you should be able to prove #2 more easily:
Bobby: If 17 is too young to vote [#1], then 14 is out of the question [#2].
Kids love this kind of stuff!
While compelling in just about any rhetorical situation (if done well), a fortiori arguments are particularly suited for situations where you don’t have all the facts or where witness accounts differ:
Lawyer Larry: Ladies and gentlemen of the jury. We’ve ruled out my client’s grandson as a suspect, a young and able-bodied runner, because he was too far away at the time of crime. [#1] What makes us think, then, that my client, who is turning 85 and uses a cane, could have dashed to the crime scene and been back to the park in time to cheer on his grandson in the race? [#2]
Here Larry creates reasonable doubt by showing that it’s harder for an old man to move around than for a young man. If the old man and young runner were at the same venue (the race) and the young runner didn’t have time to commit the crime, then it’s easy to believe that the old man also didn’t have time. Voila!
Sometimes, though, a fortiori arguments are good for a laugh:
Cop: This opera singer is dead. [#1]
Witty Detective: I guess the fat lady won’t be singing tonight. [#2]
But they have a serious side, a version that can be particularly powerful (and poetic):
“…if the invention of the ship was thought so noble, which carrieth riches and commodoties from place to place [#1]…how much more are letters to be magnified, which as ships pass through the vast seas of time, and make ages so distant to participate of the wisdom, illuminations and inventions, the one of the other. [#2]”
– Francis Bacon, “The Advancement of Learning”
When constructing a fortiori arguments it’s important that your second proposition be proportional to your first. That is, if you’re claiming something too little or too obvious (like the dead singer example) then you look like a weak rhetor. A hit to your ethos. But if you’re claiming too much, your argument seems unbelievable. For example:
Julia: If you think it’s right to take care of your family [#1], then you must also agree that it’s moral for the government to take care of your family [#2]—since a government-run welfare state is just an extension of ourselves.
Not quite, Julia. Even if I accept the first premise, there are any number of good reasons not to accept the second. The problem here is that Julia isn’t arguing “from the stronger.” She’s arguing from a weaker premise and trying to get me to accept a less likely position.
Her argument also raises one more caveat about a fortiori arguments: Be sure your audience will accept your first premise. In most cases it’s best to use something immediately verifiable instead of philosophical:
Trisha: In a recent survey, 21% of people said they are leaving New York because of the high cost of living. [#1] It’s a good bet they won’t be moving to Hawaii, which has the highest cost of living in the US. [#2]
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While working through your Netflix queue or reading tomorrow’s Austin Statesman, be on the lookout for a fortiori arguments. They’re everywhere. Write them down, write your own, and pretty soon you’ll be a better rhetor.