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Is ad hominem ever valid?

rcronk

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I didn't know where to put a logic/debate/fallacy question so here it is in the "science" section.

I know that in a logical argument, the people bringing the argument to the table should be irrelevant and the argument or position itself should be able to stand on its own. But is there ever a time to question a person's motives or reliability and have that be a part of the argument? I looked at the wikipedia article on ad hominem and it talked about some exceptions being eyewitness reliability, etc. but I'm not sure how that fits (or even if it needs to at all) in a logical debate. Here's a quote from wikipedia:

wikipedia said:
Ad hominem arguments are always invalid in syllogistic logic, since the truth value of premises is taken as given, and the validity of a logical inference is independent of the person making the inference. However, ad hominem arguments are rarely presented as formal syllogisms, and their assessment lies in the domain of informal logic and the theory of evidence. The theory of evidence depends to a large degree on assessments of the credibility of witnesses, including eyewitness evidence and expert witness evidence. Evidence that a purported eyewitness is unreliable, or has a motive for lying, or that a purported expert witness lacks the claimed expertise can play a major role in making judgements from evidence.
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So in a debate in the JREF forums, for example, if a user that has been shown in the past to be unreliable or heavily biased in one direction makes a statement, is it valid to bring up their character or past posts or is that just a shortcut when working through their facts logically and leaving them out of it completely really the right way to go? I've seen it go both ways on these forums and it seems to go much better without any ad hominem arguments so I'm leaning in that direction currently. I guess the people arguing the point are usually not witnesses or experts themselves, so maybe determining their reliability is not necessary.

I welcome your viewpoints on how ad hominem fits into debate (or not) because I know many of you are very good debaters and know these things much better than I do. Or is that just an appeal to authority? :) Thanks in advance for your help.
 
An d hominem as such is never a valid argument. Who delivers a fact has no bearing on the nature of the fact.

But life is not as simple. We can question whether something that is presented in argument is actually a fact. Often arguments depend on the severity of certain effects, and we can question that, too.

In cases like those, a known bias would be a reason to carefully examine someone's claims. But knowing about the bias alone won't be sufficient.
 
Rasmus said:
An d hominem as such is never a valid argument. Who delivers a fact has no bearing on the nature of the fact.

But life is not as simple. We can question whether something that is presented in argument is actually a fact. Often arguments depend on the severity of certain effects, and we can question that, too.

In cases like those, a known bias would be a reason to carefully examine someone's claims. But knowing about the bias alone won't be sufficient.
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Thanks. It seems like it comes down to the chain of custody - where did the evidence or expertise come from originally, how reliable is that source, and who has touched/manipulated it since that moment. So if we distrust someone in that chain who is bringing facts or expertise to the table, then pointing out that they may be unreliable could be relevant but it isn't the argument itself. It could cause people to more carefully examine the chain of custody or get second and third opinions about the expertise being claimed though, right?

ETA: So, when someone cites a source, they take themselves out of that chain of custody and out of the line of ad hominem fire?

If that's true, then would the opposite of that be an appeal to authority? Trusting someone in that chain of custody without scrutinizing the evidence or expertise?
 
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It would be nice if some discussions were made without poster names at all. OTOH, I have often replied to an argument that seemed valid only to regret it later because the poster was ridiculous and his purpose was not to discuss but to cause havoc.

Ad hominem attacks are a filthy tactic with well-meaning posters, but they save you a lot of time with malevolent idiots.
 
Ad hominem attacks are never a valid way to win an argument but some people deserve them and they sure can make you feel better.
 
robinson said:
Interesting point. I see both occurring, with a curious bias mixed in.
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I've found very few unbiased sources unfortunately. But if I am only skeptical of the ones I think are biased, then I can get bit on the ones I assume are trustworthy and unbiased. So on that count, I think it's better to stay away from specifically directed ad hominem and be skeptical of all evidence and expertise.

El Greco said:
It would be nice if some discussions were made without poster names at all. OTOH, I have often replied to an argument that seemed valid only to regret it later because the poster was ridiculous and his purpose was not to discuss but to cause havoc.

Ad hominem attacks are a filthy tactic with well-meaning posters, but they save you a lot of time with malevolent idiots.
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Yes, I think ad hominem is brought up as a time saver. That doesn't make it right, but it does seem valid if you know someone has posted absolute drivel in the past - but what if they've changed?

And again, I guess one can eliminate the need for ad hominem attacks by going around the subject of the attack directly to the original source or by getting many second and third opinions to check experts. Any other comments?
 
KingMerv00 said:
Ad hominem attacks are never a valid way to win an argument but some people deserve them and they sure can make you feel better.
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I know what you mean about them being satisfying. :) So ad hominem attacks are never a way to win an argument, but can they be used to challenge the evidence chain or expertise? If so, what's valid and what's not? Where's the line?
 
rcronk said:
Thanks. It seems like it comes down to the chain of custody - where did the evidence or expertise come from originally, how reliable is that source, and who has touched/manipulated it since that moment. So if we distrust someone in that chain who is bringing facts or expertise to the table, then pointing out that they may be unreliable could be relevant but it isn't the argument itself.
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Yes. A valid reply to such an argument might be: "I agree that you argument is sound, but I doubt your premises."

It could cause people to more carefully examine the chain of custody or get second and third opinions about the expertise being claimed though, right?
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Right.

ETA: So, when someone cites a source, they take themselves out of that chain of custody and out of the line of ad hominem fire?
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Not necessarily. A poster might have a history of citing dubious sources. If a poster like pointed towards a source I might feel very much inclined to not outright trust the source.

If that's true, then would the opposite of that be an appeal to authority? Trusting someone in that chain of custody without scrutinizing the evidence or expertise?
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Not quiet. It would definitely be an appeal to authority if you were asked to trust an argument because it was made by so-and-so rather than someone else.

But if so-and-so is an authority in the filed under discussion then what he says does have some weight. But they could still be wrong, regardless of their name.

Basicially, as long as you recognize that someone could still be right (or wrong) despite of who they are, you should be safe from committing either fallacy.
 
rcronk said:
Yes, I think ad hominem is brought up as a time saver. That doesn't make it right, but it does seem valid if you know someone has posted absolute drivel in the past - but what if they've changed?
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Well, bad luck then. I won't miss them, they won't miss me. There are people "in real life" to whom I've dedicated much less time than what I'd like. It may be unfair, but I don't have time to check twice and thrice on each person to see whether they've changed or not. And frankly, no one loses from such an attitude. Not me, not the other persons and certainly not the discussion. We live in the age of pluralism where there are tons of discussions and lots of interlocutors. Saving time is much more important than missing a debate with a possibly reformed wicked person.
 
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Thanks for all of the posts. It looks like one can completely avoid ad hominem attacks during the argument itself (unless it feels good, of course :)) and just challenge premises or logical fallacies in their argument. It's more work than dismissing them, but it keeps the argument on high ground.

So, should an ad hominem argument be avoided when it comes to challenging firsthand witnesses or experts? If so, how. If not, what's the best way to challenge witnesses or experts who we think may be in question?
 
Well, what do you think of this:

in a JREF thread, a certain creationist poster claimed repeatedly that multiple selection pressures "profoundly slow" evolution. Furthermore he claimed to have evidence for that from a computer model. Of course the opposite is true, and (after some fruitless argument) I offered to bet him $10,000, to be settled by the computer model in question. He declined.

I consider that a very effective and valid argument and/or evidence against his position, but I suppose it is technically ad hominem.
 
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sol invictus said:
Well, what do you think of this:

in a JREF thread, a certain creationist poster claimed repeatedly that multiple selection pressures "profoundly slow" evolution. Furthermore he claimed to have evidence for that from a computer model. Of course the opposite is true, and (after some fruitless argument) I offered to bet him $10,000, to be settled by the computer model in question. He declined.

I consider that a very effective and valid argument and/or evidence against his position, but I suppose it is technically ad hominem.
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Has that thread reached 10,000 posts yet? From what I saw on that thread, it had a high signal to ad hominem attack ratio and it was very annoying. It really got in the way of clear debate unfortunately.

I don't know if his declining to bet would technically be an ad hominem attack. What kind of fallacy would it be to assume that he's bluffing because he doesn't take a bet?
 
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