Freakonomics Quiz: Doonesbury Logic

Here a pretty simple puzzler. Can you find a mistake in Alex‘s logic (taken from an October 9, 2000 strip)?

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The usual Freakonomics schwag to the first commenter to post a nice, quotable answer.

(Hat tip: Sparky Clark)


Michael

Not being an independent does not mean that one doesn't have a mind of his own. if p then q does not imply if not p then not q.

I believe the correct statement would be: if you don't have a mind of your own, then you are not an independent.

amateur

i'm trying to think of something to say, but i'm at a loss

Jon

My enemies enemy is not necessarily my friend. Nothing keeps independents from being as brainless as party members.

Paari Kandappan

An independent actually means you have no mind at all.

Kari

He's making an inverse error. He's saying that if you are p, then you are q, therefore if you are not p, the ellipses imply not q. That's like saying if you're from Chicago, you're from Illinois. And if you're not from Chicago, then you are not from Illinois.

Paari Kandappan

Sorry the grammar on my last post was off, here's a fixed version: "An independent actually has no mind at all."

Jon

Being in the party and being stupid are not mutually exclusive, one can not be in the party and also be stupid.

rusty

"Conversely" would require you to start with the 'then' part of the initial 'if -> then' proposition.

i.e. Alex should say, "Conversely, if you do not have a mind of your own..."

David Saphier

All independents having a mind of their own does not imply that non-independents do not have their own minds. The first statement says nothing about non-independents.

Anjan

Being is confusing the meaning of independent. Independent is being used in two different ways. One as a political party and one as having a mind of your own. The latter is not exclusive to your party.

Erin

She's using bad conditional logic. If independent -> mind of your own = if no mind of your own -> not independent. From the first statement, you can't infer anything about people who AREN'T independent.

Max B. Dorsey-Gordon

It is an example of false induction.
This is a crow and it is black; that is a crow and it is black; therefore all crows are black

Ari

"If you're an independent, then you have a mind of your own," doesn't imply the inverse, "If you're not an independent, then you don't have a mind of your own." Here's a more obvious example of this logical fallacy: "All fish swim. Michael Phelps is not a fish. Therefore, Michael Phelps doesn't swim."

Todd

Alex, its the contrapostive, "NOT having a mind of your own implies that you are NOT an independent", that is equivalent to "being and independent means that you have a mind of your own" not the converse.

Of course, many independents don't have a mind at all, let alone a mind of their own.

Cait

equivocation!

Derick

“All fish swim. Michael Phelps is not a fish. Therefore, Michael Phelps doesn't swim.” I now have a new example for this type of logic.

Sean

The Law of the Excluded Middle may work well in the calculus, but false dilemmas have no place in debate.

Jason

"If you have a political party, you're motivated by a certain ideology."

"What does that say if you don't?"

Arithmomaniac

If Independents have minds, the logical corollary would not be the inverse (non-independents don't have minds), but the contrapositive (someone without a mind must not be Independent.)

Jrrd

False syllogism. Too bad a lot of others got it before me.