Thursday, March 13, 2008

Ad hominem

I've been thinking recently about what constitutes an ad hominem. Generally speaking, an ad hominem dismisses an argument or a position because of the person who holds it. And being a fallacy, it is best avoided.

But it seems like there are times when it is okay to ignore what is said because of who says it. If a person has consistently shown herself to be a liar, it is fine to say "don't trust what she says." That's not the same as saying that what she said was false, just that the source is not trustworthy. And I don't think this qualifies as ad hominem, since we are not denying what is said, just rejecting the trustworthiness of a source.

What if we expand on the case. Let's say we know a person who consistently seeks the truth, and then gives us the opposite report. Consider a person who knows more about a subject than any one else, yet repeatedly declares publicly what he knows to be false. In this case, it might be better to go beyond "don't trust what he says" to "what he says is false" and to say this simply because of who said it. This seems like a intellectually responsible thing to do, even though it is structurally similar to an ad hominem. Perhaps in cases of consistent liars, it is best to reason from an ad hominem. Real-world circumstances might prevent us from ever having a clear case of this, which is why this reasoning probably shouldn't be advocated in any case. But it does seem possible that such a case could arise.

Fallacies are fallacies because they give the appearance of validity or reasonableness but can't be trusted in all cases. Even one counterexample works. But by restricting the scope of when it is permissible to employ it, I think we could find a non-vicious use of ad hominem.


Dan said...

As you already mention, there are cases where the trustworthiness of the person matters.

The clearest case is in a legal context of testimony, where the moral character of the witness is often inspected in order to make a judgment about whether or not the testifier should be taken as credible. If his or her moral character is found to be lacking, then his or her testimony is taken to be unreliable. It’s of course granted that he/she could be telling the truth, but what’s at issue is whether or not one can trust the testifier’s words.

I guess the same thing could be extended to your case. In such a case, it’s something very specific about both the person in question and what he or she says (namely, that the person is a habitual liar about subject X), other than mere prejudice on the part of the interpreter.

I think you’re right; this is not a clear cut case of an ad hominem fallacy. Even the other famous fallacy, tu quoque, has this more complicated, context sensitive nuance.

Anonymous said...

Socrates is said to have argued ad hominem. And that is not thought of in a negative or derrogatory sense. What is meant is that he addressed his reasonings and arguments toward people, not simply or more importantly toward thoughts or theories. His aim was to "improve the souls of others," those with whom he was having a conversation. He wasn't, for example, just interested in finding g out exactly what piety was; he was interested in whether Euthyphro indeed knew what piety was well enough to be warranted in going forward with a prosecution against his father in order to preserve his family from religious pollution.

That is not at all the sense in which critical thinking or logic text books discuss an ad hominem fallacy. In addition, it is only a careful logic textbook that refers to it as ABUSIVE ad hominem, indicting that there are instances of ad hominem reasoning, like "don't believe that person, he is a notorious liar" that are not fallacious. True they are attacks on the character of the person, but when warranted they are not forms of fallacious reasoning. As well it is true that sometimes when we discount a liar we discount a time when they happen to be telling the truth.

tpy said...


I think of a tu quoque is a subspecies of ad hominem. The court case gives rise to a similar instance of what I discuss.

Anon 10:23,

You are right to point out that I am talking about abusive ad hominem. I left out the word 'abusive' since I was talking about the fallacious ad hominem. I think there is a very good way in which arguments can be ad hominem, in that they work from premises held by the audience. In this sense, more philosophy should be ad hominem, I think.

But there is still a case that I was trying to point out where one rejects an argument because of who holds it, and this does not fit nicely into either of the set of abusive ad hominem or audience-adjusted ad hominem.

Tom said...

What are the roles of empiricism and rationalism in this issue? It seems as though the more rigid view that the truth is the truth no matter who espouses it or the source by which we attain it coincides with a rationalistic view of logic/arguments, whereas believing it to be true based upon our experience(s) of our source would seem to coincide with empirical focus.

Needless to say, it seems as though all of the issues discussed pertain to the epistemological certainty that the premises and conclusion are true (can we KNOW that it is true) instead of whether or not the thing-in-itself is true independent of the knower. Unless Berkeley's not as big of an idiot as he seems.