by Paul Braterman
R: Sagan warns us against fallacies. But is exposing fallacies enough to shield us from the demons?
I had been waiting for a quiet moment to write about this, but there isn't going to be a quiet moment, so now will have to do.
Debaters regularly accuse their opponents of using fallacies. These can be formal fallacies, such as simple errors of logic, or informal fallacies, such as appeal to authority, ad hominem and strawman arguments, among others. If a piece of reasoning depends on any of these fallacies, so it is claimed, the conclusion does not really follow from the premises, and while it might still be true we have not been given any good reason to believe it.[1] And so books that discuss logic, and science-promoting blogs (including one I follow), regularly include descriptions of informal fallacies, with stern instructions to avoid committing them.
In an article entitled The Fake, the Flimsy, and the Fallacious: Demarcating Arguments in Real Life, Maarten Boudry, Fabio Paglieri and Massimo Pigliucci (henceforth BPP) challenge this view. BPP is written for the perusal of trained philosophers, which I am not, but I use it here as a jumping off point, while mixing in further content of my own.
BPP apply what they call the fallacy fork test to accusations of informal fallacy; either the reasoning is obviously erroneous, in which case no one would really use it, or else it is not obviously erroneous in context, and we still have all the work to do. In the first case, formal analysis is redundant; in the second, the facts of the matter need further consideration. So naming and shaming the particular kind of fallacy is either unnecessary or uncalled for. I agree, and suggest that we drop the label "fallacy" for such informal arguments, since to make the label stick we have to show on other grounds that the argument as used really is fallacious. The discussion made me think of my own reflections on formally valid logical arguments, which only work because the conclusion has actually been accepted in advance, otherwise we would not have accepted the premises. In both cases, the formal or semi-formal reasoning, while seemingly at the heart of the argument, is an unnecessary elaboration, and we can cut out the middleman.
Going beyond this, it is becoming increasingly clear that the logical is only one aspect, and not usually the most important aspect, of an argument. More important are the heuristic and rhetorical aspects; will the reasoning point us towards a way of acquiring new knowledge, and how useful is it in the attempt to persuade our opponents to change their minds. (In passing, I suggest that if our objective is to persuade others to change their minds, we are not arguing in good faith, unless we are at least in principle open to the possibility that we too might change ours.)