When is ad hom a fallacy?

GreedyAlgorithm said:
JetLeg brings up the question of whether or not learning an arguer was drunk at the time he made his argument should lead us to believe the argument is less likely to be true in this thread. There's something intuitively compelling about the claim that it should, and something else compelling about the claim that it's just an ad hominem.

Here is the difference:

The substance of the argument itself screens off the drunkenness of the arguer. Obviously if the argument is sound then it is sound regardless of the state of the one making the argument. If however we do not know the argument itself, then knowing that the arguer was drunk is very relevant evidence that once we know the argument, we are more likely to find it fallacious. In terms of causality, being drunk is one possible cause of making bad arguments, but is not the cause of any instantiated argument being fallacious. In the causal graph, we'd see

DRUNKENNESS ==> SPECIFIC ARGUMENT MADE ==> FALLACIOUS ARGUMENT

as one subset of the graph. Until we observe the value of SPECIFIC ARGUMENT MADE (i.e. hear the actual argument), if we observe that DRUNKENNESS is higher, we compute that FALLACIOUS ARGUMENT is higher. But if we know the actual value of SPECIFIC ARGUMENT MADE, it screens off the "probability flow" from DRUNKENNESS to FALLACIOUS, and knowing that DRUNKENNESS is higher no longer raises FALLACIOUS.

And so it is ad hom to continue to use evidence of drunkenness as evidence against the argument once you know the argument, but it is not ad hom before. This is why it's fine to decline even reading another of Ray Comfort's arguments - it's so unlikely that the argument is any good, it's a better use of your time to do other things. Did you actually read one, though, the mere fact that it is Ray Comfort's will no longer help you guess whether the argument is good or bad - you know too much now.

(or read this on argument from authority: Argument screens off authority)
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P is the statement "The argument of the drunk is probably fallacious".

According to your claim, before you know the actual argument, P is true. But suddenly, when you know it, then suddenly you have to forget that P is true? It is absurd - if you know P is true, you cannot claim suddenlly you don't know P to be true.
 
Ignore all the arguing drunks you like, JetLeg. I promise, you won't miss a thing by doing so, and absolutely no one will mind.
 
Beerina said:
Ahhh, good ol' Winnie.



Lady Nancy Astor: Winston, if you were my husband, I'd put arsenic in your morning coffee.

Churchill: Madam, if you were my wife, I'd drink it.
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Dave Barry (IIRC) had a couple good parodies of this.

"Madam, if you were my wife, I'd hit you in the face."

"Madam, I may be drunk, but *bleargghhh*" all over her dress.
 
linusrichard said:
I don't think it is. But maybe I was unclear - I'm not talking about the argument - I'm talking about the premises.


Right, but I'm talking about the premises here. And obviously the drunkenness of the proponent doesn't affect the truth or falsity of the premise, but - if we don't know the truth or falsity of the premise, we may consider the credibility of the proponent in deciding whether or not to accept it as true or false. And when considering the credibility of the proponent, we can look at the drunkenness of the proponent as one piece of evidence that goes to credibility.

Let me come up with some clumsy examples:
Alan walks up to you, drunk. You have no idea where he lives. "Can I take you home, Alan?" "Sure, take me to 123 Aspen." I would take him to 123 Aspen.
Bob walks up to you, stone sober. You are pretty sure he lives at 123 Birch. "Can I take you home, Bob?" "Sure, take me to 132 Birch." I would take him to 132 Birch.
Carl walks up to you, drunk. You are pretty sure he lives at 123 Cedar. "Can I take you home Carl?" "Sure, take me to 132 Cedar." I would probably take him to 123 Cedar.

Now, these don't look like arguments, which is why my examples are clumsy, but let's turn them into arguments:
1. Major premise: You should take me to the address which is my home.
2. Minor premise: The address which is my home is ______.
3. Conclusion: You should take me to _____.

Now, all three arguments are perfectly valid, and their validity can be judged without reference to the men's drunkenness. But we see that when we evaluate each man's minor premise, we can take the drunkenness into account. In Alan's case, we have no better alternative, so even though he is drunk, the best we can do is assume his minor premise is correct. In Bob's case, we have a reason to think he is wrong (our previous idea about his address), but a better reason to think he is right (a sober person is unlikely to misstate his address). And in Carl's case, we have a reason to think he's right (a person knows his address), but a better reason to think he's wrong (our previous idea about his address combined with the possibility that his drunkenness has caused him to transpose numbers).

...

Of course not. But that's not what I'm saying. What I'm saying is that we can consider drunkenness in evaluating the probability that the conclusion is correct, not (obviously) because it is relevant to the validity of the reasoning, but because it might be relevant to whether we trust the premises. Just as Bob and Carl presented us with identical situations, other than the drunkenness, but it was reasonable to reject Carl's conclusion and accept Bob's, based on that difference.
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Good post. I agree with that.

But even with regards to the validity of the drunk's logic - there is a larger probability that his arguments will be invalid.


I will give a better example than a drunk - the URL
http://jmm.aaa.net.au/articles/13209.htm

The arguments there are bad ones. If you read 5 arguments from there, are you justified in becoming tired and coming to the conclusion that the rest of the arguments will have bad logic as well? Yes. (I think it just analogous to my example of drawing lots of black balls from a box, and concluding that probably the next one will be also black. )

What I said above is common sense, I think. If a certain person is famous for making arguments with flawed logic all the time, it is probable that his next argument will also have bad logic.

The step that is more problematic is to take a specific argument that he makes and to claim that since it is an argument by such a person, there is a high probability that this argument is false.
 
slingblade said:
Ignore all the arguing drunks you like, JetLeg. I promise, you won't miss a thing by doing so, and absolutely no one will mind.
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Slingblade, the answer to my question is not that trivial, so you do not do justice to me, dismissing derogatingly.
 
Greedy Algorythm actually made a really good point, and I think it resolves the question.

The argument

The vast majority of X's arguments are invalid
P is an argument by X
---
It is probable that P is invalid.

Is a valid inductive argument, and not an ad hom. However, when one actually judges the specific argument P, since it is possible that it is valid, then one has to judge by its own merit, and not by association with X. It is a bit complicated to put in words, but can be easily explained using the analogy of black and white balls :


If there is a box with 99% black balls, there is a 99% probability that a randomly taken out ball will be black. However, when you take a ball, and try to determine whether it is a black ball or not, you use your sight - you do nto use the probability. You cannot take out a ball, and not judge whether it is black or white "on its own merit". You cannot take a white ball, look at it and declare "there is 99% probability that this ball is black"!!

And linusrichard has a sound point as well, with regards to the premises.
 
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