And nobody said otherwise -- for the core argument.

But in real life we don't usually know whether the thing (let's call it A) itself that an argument tries to prove is true.

We only know that the argument in favor of A is formulated correctly (follows its premises correctly, etc).

Regarding A though, there might be other premises we haven't checked (and weren't mentioned in the argument), other facts that invalidate it, etc.

Thus it is enlightening to know if an argument for A is being made hypocritically, to evaluate the possibility of A being true in a wider context.

E.g. if I say "A is good for everybody, for X,Y,Z reasons" and I do the opposite of A, then the possibility of A really being good for everybody is somewhat lessened by the prior that "the person proposing A does not follow A".

This is because:

a) nothing guarantees that X,Y,Z (the things mentioned in the argument) are enough to prove that A is good for everybody.

b) the fact that someone proposes A but does the opposite, adds credence to the possibility that there are benefits from NOT following A.

Heck, even if the argument is that "A is good for you for X,Y,Z" and it's correct, someone that knows X,Y,Z (since he put forth the argument) but does not follow A, might know something like A+ or B that's even better, and tries to sell me short.

I would say it's a fallacy to harp on logical fallacies; it's not as if everyone has infinite time to convert all arguments to syllogisms. The common list of logical fallacies entered Western culture from the ancient Greeks but shouldn't be taken with religious fervor.

I'm just convinced coldtea is wrong. The fallacious use of logical fallacies has taken over far too much of public debate.

The common list of logical fallacies entered Western culture from the ancient Greeks but shouldn't be taken with religious fervor.

Sure. Let's apply them with logic.

That sounds like logic, but it makes much less sense than it sounds. So you're saying it's good to examine the hypocrisy of someone's argument, because of the possibility that there's contradictory facts or implications that the arguer is holding back on us? Not only is that also ad-hominem it's a fuzzy half-logical ad-hominem.

Yes.

>Not only is that also ad-hominem it's a fuzzy half-logical ad-hominem.

It's also correct, and a pragmatic way to find hidden motives in real life.

You're contradicting yourself right here, in a way that seems to indicate that you don't understand the important difference between these two circumstances.

Something that's pragmatic is merely mostly correct or most of the time correct. One could say the same thing about racial stereotypes in the US -- which is to say that heuristics shouldn't be treated as an argument. It's only at best a starting point. Quitting at that point is the worst kind of mental laziness.

"It's good for you to not smoke. Now excuse me while I take my smoke break."

That what I said doesn't always hold?

Of course it doesn't.

That's why I wrote about possibilities, and only said that the prior that the person preaching X doesn't follow X "somewhat lessens" the possibility that X is true.

I never said that someone "preaching X and doing the opposite" proves that X is not true.

If I had said that, your example would be a valid refutation. But I haven't, and it's only attacking a straw man.

Besides, the only reason that your example case seems obviously wrong to you is because you're taking as a given what you are supposed: you already know that smoking is bad.

If you didn't, and someone said to you "smoking is bad for you", while he himself was smoking, you would be justifiably suspicious to consider whether it's not actually bad, and the other person is lying or hiding something from you (e.g. to keep all the cigarettes for himself).

The correct answer is to independently validate the claims, or evaluate the merits of an argument on their own ground. That's tedious and often not worth the effort, and that's OK. We use heuristics all the time -- you don't ask your friend for his proof, because you use the heuristic of trust instead. But at least acknowledge that it's a heuristic and stop trying to claim it as a solution.