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My Absent Career 13: Critical mass

Last updated on 18 Jan 2023

Having taught critical reasoning and studied the usual logic for philosophy undergrads, I felt that I had a pretty good understanding of logic and reasoning, at least without getting into modal logics and other such aberrations. Not for the first or last time I mistook confidence for competence.

Neil Thomason, my PhD advisor, had a grant from the US intelligence organisation IARPA, their version of DARPA, to work out ways to teach critical reasoning skills to intelligence analysts in the wake of the debacle over weapons of mass destruction. Spoiler, we had. variable success in the development of these techniques. We were basing our research on Tim van Gelder’s method of diagramming arguments and software that he designed to use it.

In between trying to wrestle the paperwork of PacCom (and I am not as worried as I was that the US will invade Pacific nations, as they could never complete the paperwork in time), I learned from Neil about work done on fallacies, beginning with Charles Hamlin’s Fallacies*. It was obvious that not only was there no canonical list of fallacies from Aristotle to today, but many of the fallacies in those lists were not, actually, fallacious in some contexts. For example, ad hominem is not a fallacy if the character of the interlocutor goes directly to the truth of their claims (think Trump).

But even more surprising was work done that showed that teaching fallacies actually inhibits rather than assists in learning how to reason critically.** There are many reasons, but the vagueness and contradictory presentations of why a fallacy is fallacious number among them. After all, how many ways are there of being wrong? In mathematics there is no canonical list of errors, there are just errors. Similarly in logic: the so-called formal fallacies are just a list of common misuses of logical operators and framing. But the informal fallacies are legion and not at all based upon a coherent set of rules of reasoning.

Moreover, there is a psychologistic aspect to this: people tend to use fallacies as post-hoc support for attacks upon an opponent’s arguments, never applying the same standards to one’s own reasoning. In short, fallacies are tribal weapons. If you doubt this, teach reasoning to students using political or religious examples.

Indeed, Hugo Mercier and Dan Sperber have even argued that reasoning evolved for the purpose of justifying prior conclusions rather than prospective argument to the best inference.† Not sure how far I would go with this, as at least some reasoning is prospective (how to I solve this problem) but this blends well with literature on reasoning under uncertainty (Gigerenzer and collaborators).¶

* Hamblin, Charles Leonard. 1993. Fallacies. Newport News, VA: Vale Press.

** See, for instance

Hitchcock, David. 2017. “Do the Fallacies Have a Place in the Teaching of Reasoning Skills or Critical Thinking?” In On Reasoning and Argument: Essays in Informal Logic and on Critical Thinking, edited by David Hitchcock, 401–8. Argumentation Library. Cham: Springer International Publishing.

Hundleby, Catherine. 2010. “The Authority of the Fallacies Approach to Argument Evaluation.” Informal Logic 20 (3): 279–308.

Zeidler, Dana L., Norman G. Lederman, and Stephen C. Taylor. 1992. “Fallacies and Student Discourse: Conceptualizing the Role of Critical Thinking in Science Education.” Science Education 76 (4): 437–50.

† See:

Mercier, Hugo, and Dan Sperber. 2011a. “Argumentation: Its Adaptiveness and Efficacy.” Behavioral and Brain Sciences 34 (02): 94–111.

———. 2011b. “Why Do Humans Reason? Arguments for an Argumentative Theory.” Behavioral and Brain Sciences 34 (02): 57–74.

†† See:

Chase, Valerie M., Ralph Hertwig, and Gerd Gigerenzer. 1998. “Visions of Rationality.” Trends in Cognitive Sciences 2 (6): 206–13.

¶ The literature is vast, but here are the main pieces

Gigerenzer, Gerd. 2000. Adaptive Thinking: Rationality in the Real World. Evolution and Cognition. New York: Oxford University Press.

Gigerenzer, Gerd, and Daniel G. Goldstein. 1996. “Reasoning the Fast and Frugal Way: Models of Bounded Rationality.” Psychological Review 103 (4): 650–69.

Gigerenzer, Gerd, and Reinhard Selten. 2001. Bounded Rationality: The Adaptive Toolbox. Cambridge, Mass.; London: MIT Press.

Gigerenzer, Gerd, and Thomas Sturm. 2011. “How (Far) Can Rationality Be Naturalized?” Synthese 187 (1): 1–26.

Gigerenzer, Gerd, Peter M. Todd, and the ABC Research Group. 1999. Simple Heuristics That Make Us Smart. Oxford; New York: Oxford University Press.

Todd, Peter M., and Gerd Gigerenzer. 2000. “Précis of Simple Heuristics That Make Us Smart.” Behavioral and Brain Sciences 23: 727–41.


  1. I’ve thought for a while that many/most/all of the “standard” fallacies should be seen as overzealous or otherwise inappropriate application of perfectly respectable reasoning heuristics. Ad hominem, obviously — in arguments about the real world, you have to justify your premises empirically, which frequently has to rely on someone else’s word, thus the prior credibility of one’s source is relevant, and factors like demonstrated stupidity or dishonesty can rationally make us discount that. Or consider the Fallacy of Affirming the Consequent: if P is known to be a frequent cause of Q, then concluding P from observing Q is a perfectly valid (if probabilistic) induction. The fact that these heuristics so often yield true conclusions is what makes them tempting to overuse (overenthusiastic meta-induction?).

    • This is the point of comments of the older logicians like Whateley’s:

      After all, indeed, in the practical detection of each individual Fallacy, much must depend on natural and acquired acuteness; nor can any rules be given, the mere learning of which will enable us to apply them with mechanical certainty and readiness: but still we shall find that to take correct general views of the subject, and to be familiarized with scientific discussions of it, will tend, above all things, to engender such a habit of mind, as will best fit us for practice.

      Book III

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