Tuesday, March 12, 2013
Statistician John Cook made an interesting observation some time back regarding certain instances of the ad hominem fallacy:
"A statement isn't necessarily false because it comes
from an unreliable source, though it is more likely to be false
[bold in original]." Cook elaborates:
Some people are much more likely to know what they're talking about than others, depending on context. You're more likely to get good medical advice from a doctor than from an accountant, though the former may be wrong and the latter may be right. (Actors are not likely to know what they're talking about when giving advice regarding anything but acting, though that doesn't stop them.)Nobody knows everything, and our division-of-labor society makes the use of guesses about the knowledge level of others unavoidable. On top of that, gathering additional data takes time and effort. (This last might help explain why ad hominem attacks often succeed.)
Ad hominem guesses are a reasonable way to construct a prior, but the prior needs to be updated with data. ...
While one cannot necessarily gather additional data every time a stranger makes a point or offers unsolicited advice, one can make the most of the data he already has by attempting to see how some proposition fits in with the rest of his knowledge. Part of this is considering whether the person has offered any kind of a sound basis for, or means of checking his argument.
What to do, though, when what you are hearing comes from out of the blue and is offered arbitrarily or on some patently absurd basis? Even a parrot can make sounds resembling true statements. I ignore such advice until and unless I hear it coming from another, better source. (One could say that the fact that the person indulged in the arbitrary was sufficient data regarding the person, but that the new source may offer additional data on the point he raised.)
Regarding such claims, Ayn Rand put it best when she stated, "Since an arbitrary statement has no connection to man's means of knowledge or his grasp of reality, cognitively speaking such a statement must be treated as though nothing had been said."
Some individuals habitually make arbitrary statements. While dismissing everything they say is not good formal logic, generally ignoring them can save enormous amounts of time and mental energy.