Learn Logic with Beavis and Butthead!

A work in progress, where our two friends exemplify logical fallacies, types of causation and other cool stuff. Quotations are from memory, and so may not be entirely accurate, e.g. I may have substituted “buttmunch” for “buttknocker”....

Circular definition

This is where you include the concept you are defining in the definition of that concept.


Butthead: Shut up, bunghole!
Beavis: What's a bunghole?
Butthead: A bunghole is what you are, bunghole!

Fallacy of Accident

Assuming that a generalisation will hold in every case.


Butthead: They must be cool, they're from Seattle.


Here is a similar problem involving causality.


Butthead: Hey Beavis, I've just worked out that all of our ancestors scored. That means we're gonna score!

Converse Fallacy of Accident(?)

Making a generalisation from insufficient evidence.


Storekeeper: Hello, Maximart. We've got a robbery in progress
Police : Are they armed?
Storekeeper: Er...of course they're armed. Aren't all kids armed?


A related problem with overgeneralisation occurs when we observe a cause p and effect q and erroneously conclude pq (If p then always q), ignoring the fact that there may be other causes; e.g., (prs)⇒q. Here, our friends are watching Morgan Spurlock recieve an Oscar for Supersize Me.


Butthead: Whoa, check out that chick.
Beavis: Yeah, who's that fartknocker she's with?
Butthead: I heard about this dude. He got famous for, like, eating a lot for thirty days. Yeah, and once your famous …
Beavis: You get to eat more!
Butthead: Dumbass. You get chicks.
Beavis: I was gonna say that next.
Butthead: We should do that.
Beavis: I was gonna say that next.


Equivocation means many things, but is often taken to mean using a word in a different sense to that which was intended. In fact the word "equivocation" is pretty equivocal.

(Beavis, under the influence of a music video, is “dancing” on the sofa.)


Butthead: Get down, Beavis!
Beavis: I am getting down!

Circular causation

A chicken and egg situation. Not always the result of faulty logic, of course—life is often like that, as Butthead demonstrates here …


Beavis: How come Tom Petty's on TV?
Butthead: Coz he's famous, dumbass.
Beavis: Yeah, but how come he's famous?
Butthead: Coz he's on TV, buttmunch!
Beavis: Yeah, but how come he's on TV?

and so on …

Syntactic Ambiguity and the Problems of Parsing

"Parsing" is a word familiar to computer scientists, logicians and people like me who had a very traditional education in English, part of which involved breaking down sentences to see how their component nouns, verbs and so forth went together. In everyday life, we do this effortlessly and unconsciously (a fact which has constantly intrigued linguists) but occasionally we run into a phenomenon called syntactic ambiguity. For example, does the sentence “Moving machinery can be dangerous” mean that machinery which is moving can be dangerous, or that it can be dangerous to move machinery? Parse that wrong and you can lose an arm. Here's an example from Beavis and Butthead's interview with Rolling Stone; there's an obvious confusion between Rolling Stone and The Rolling Stones, but the syntactically ambiguous phrase here is “like Mick Jagger”.


Butthead: Uh...like, are you really with the Rolling Stones?
Charles Young: I'm with Rolling Stone, the magazine.
Butthead: So, uh, do you get lots of chicks?
Beavis: Hey, Butthead, when chicks find out we know someone with the Stones, we'll get some helmet. Huh-huh, huh-huh.
CY: I'm with the magazine Rolling Stone. I'm a writer, not a musician.
Beavis: Wuss.
Butthead: So you don't get any chicks?
CY: Not like Mick Jagger.
Beavis: Mick Jagger's not a chick.
Butthead: He didn't say he was a chick, Beavis. He said he doesn't get chicks.
Beavis: He said he doesn't get chicks like Mick Jagger.
Butthead: That's right. Not like Mick Jagger.
Beavis: But Mick Jagger's not a chick.
Butthead: Don't make me kick your ass again, Beavis.


A couple of extras—not really to do with logic, but profound philosophy all the same.

Butthead on Legal Positivism

The law rules.

Beavis on the philosophy of language

Words suck.

Butthead on Eudaimonia

Counsellor: What do you want out of life?
Butthead: I wanna score.