More on the ad hominem “fallacy”

In my previous post I argued that ad hominem and tu quoque arguments are not always fallacious. I want to be clear that I am not saying, to those who claim they’re always fallacious, “Yeah, you’re right, but you’re a bunch of eggheads, so I’m gonna ignore you.” I’m saying, “You’re wrong.”

Now dweebs with no intellectual self-confidence will say, “Dear God, you can’t disagree with textbooks, man! They’re textbooks!

I can, in fact, disagree with textbooks when they make statements that are ragingly moronic. And I did so in my last post.

Today I want to provide a different, more explicitly rigorous argument refuting the notion that argument ad hominem is always fallacious. I will do this by providing an argument that is both ad hominem, and logically sound. I will also note, for those who collapse in spasms of fear at the idea of disagreeing with actual textbooks!!! that the kind of argument I am going to present is common in the academic literature, including Economics, Psychology, and, hilariously, Philosophy. The Philosophy one is hilarious because the fuck-witted “Ad hominem is a fallacy!” stuff appears in textbooks for Logic classes, which are typically taught by… Philosophy departments.

Here’s the example argument, casual version:

“Joe said that a meteor is bound for Chicago and will kill everyone in the city in an hour or so. Yet he’s calmly sitting here in Chicago with his feet up on the ottoman, sipping a Riesling. So obviously there’s no meteor.”

This is good enough to make my point for casual readers. (For those who like to dot all the i’s and cross all the t’s, more below.) I’m refuting Joe’s assertion not by attacking his assertion (not directly), but by stating something about Joe. That is, speaking precisely, an argument ad hominem – “against the man” – and the argument is valid, not fallacious.

Just for thrills, let’s disassemble it and lay all the parts out. I am going to be careful but not anal-retentive about it; professional logicians are welcome to fill in the blanks even more carefully if they want to.


1. Joe wants to live as an overriding priority. (He may also want other things, but remaining alive is priority numero uno.)
2. Joe is capable of assessing evidence pertaining to the existence and trajectories of meteors (note that if he’s not, nothing he says about the alleged meteor is credible anyway), such that he will believe a meteor is approaching if and only if there is evidence that a meteor is approaching.
3. Joe knows of at least one way to get beyond the meteor’s blast range, and to do so soon enough to remain alive.
4. Joe knows that, if there is a meteor, he will live if and only if he gets outside the blast range soon enough.
5. All methods for being outside the blast range soon enough require that Joe begin to travel immediately.

First conclusion, which follows from 1, 3, 4, and 5:

6. If Joe believes there is an impending meteor, he will begin to move immediately.

Second conclusion, which follows from 6 and 2:

7. If the evidence suggests there is meteor approaching, Joe will begin to move immediately.


8. Joe is not moving; he is calmly sitting on his complacent ass in his Lakeside Drive apartment.

Third conclusion, which follows from 7 and 8:

9. The evidence does not suggest there is a meteor approaching.

Let’s re-write 7 – 9 more tersely:

A. If there is meteor evidence, Joe is moving.
B. Joe is not moving.
C. Therefore there is no meteor evidence.

If someone tells you this is an ad hominem fallacy, your only option, as a civilized individual, is to give them a wedgie. There’s nothing else you can really do.

The argument is not fallacious. It is correct.

Again, I want to emphasize for the intellectually pious that the foregoing kind of argument is entirely standard in various branches of the academic literature.

Additionally: If you say X is true because a textbook author asserted it, you’re making an ad hominem argument. This variant of it is usually dubbed “appeal to authority,” but it’s simply the other side of the same coin. In other words, ad hominem is usually interpreted to mean,

“(Something about the author of an argument) ➞ the argument is wrong.”

While an appeal to authority is simply,

“(Something about the author of an argument) ➞ the argument is right.”

Therefore, those who would claim that ad hominem is a fallacy, and cite textbooks as support for this claim, are, in technical terms, fucking themselves over. You tell me, doofuses: Are ad hominem arguments valid or not? Double bind, bitchez!

* * * * * * * * * * * * * * * *

Xtra credit for nerdlingers: Put the A – C argument above in proposition-contrapositive form.


Using symbolic logic with the arrow (➞) indicating implication and tilde (~) meaning “not”:

The statement

A ➞ B

implies the contrapositive statement

~B ➞ ~A.

For example,

If something is a cat, then it is a mammal.
If something is not a mammal, then it is not a cat.


Meteor evidence ➞ Joe is moving.
Therefore, by the contrapositive:
~Joe is moving ➞ ~Meteor evidence.


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