Praxeology’s insistence on verbal deduction is just a cover for bad logic
Praxeological reasoning includes a substantial amount of invalid argument, of two kinds: arguments about mental categories whose conclusions we accept because while they do not follow from the premises, they accurately describe a priori human knowledge; and arguments about economics that do not follow from their premises and should not be accepted, because they are inaccurate and promoted for ideological reasons. This post is about the first category.
The other day, I related that defenders of praxeology resist formalizing their propositions, which seems indefensible for a body of knowledge that claims to be based on deductive logic. Since the burden of demonstrating the logic of a system is on those who claim that it is logical, I suggested that it is fair to dismiss praxeology on the grounds that its adherents decline to take the simple step of formalizing their arguments.
I cited this Rothbard article which defends against the formalization challenge. After verbally presenting a series of statements that he claims are logically related, Rothbard challenges the skeptic to formalize his informal reasoning, suggesting that it cannot be done, and would anyway not be useful:
let the reader take the implications of the concept of action as developed so far in this paper and try to place them in mathematical form. And even if that could be done, what would have been accomplished except a drastic loss in meaning at each step of the deductive process?
Rothbard goes on to argue against an overly formalistic approach to economic formulas, which is not the issue. The challenge is that the alleged logic of praxeology is not logic at all, and the issue is, as Rothbard formulated it, “the process of deduction; why are the means verbal rather than mathematical logic?”
Rothbard’s propositions can, of course, be formalized, and doing so will demonstrate that the deductions are either invalid arguments or trivial restatements. Maybe I’ll do some in a follow-up post.
Most of the propositions that Rothbard advocates in this essay appear unobjectionable as propositions. But this is not because they follow from the primary axiom — that individuals engage in conscious actions toward chosen goals. It is because they are statements about how our minds work, which we know are true based on experience and introspection.
So, Rothbard argues that from the fact that individuals engage in conscious actions towards chosen goals, it follows that the individual made a choice of means — which from context, appears to include instruments, material resources and time.
Rothbard seems to be arguing from an existential proposition to a statement about some definite individual. Let’s abstract away from this error, and translate “the individual made a choice of means” into an existential statement. The argument is therefore:
(1) Individuals engage in conscious actions toward chosen goals. Therefore,
(2) Individuals engage in conscious actions toward chosen goals by way of chosen means.
(2) is completely true, but it doesn’t follow from (1) unless we assume that part of the meaning of “action” involves the use of means, the way part of the meaning of “bachelor” is “unmarried”. If we do assume this, then the praxeological deduction is trivial, and praxeological “deduction” includes steps that are merely elaboration of definitions. If we built a worldview based on the premise that some people are bachelors, and claimed the deduction that some people are unmarried as an insight, we cannot claim to have uncovered a science of bachelorhood.
If (2) is not just a definition of some words in (1), then no form of logic permits the derivation of (2) from (1). We would need an additional axiom to make it follow, such as (3):
(3) If e is an event in which an individual consciously does an action in order to bring about a goal, then e involves the use of means.
Intuitively, (3) makes a lot of sense. It is possible to construct an argument using (1), which is observationally true, and (3), which is intuitively correct, as premises, and deduce (2):
(1 restated) There is an event in which an individual does an action, the individual is conscious of the action, and the action is directed toward a goal.
(3) If e is an event in which an individual does an action, the individual is conscious of the action, and the action is directed toward a goal, then e involves the individual using means. Therefore,
(2 restated) There is an events in which an individual does an action, the individual is conscious of the action, the action is directed toward a goal, and the event involves the individual using means.
Unlike Rothbard’s presentation of the praxeological “deduction,” this deduction is valid. It is not part of Rothbard’s praxeological theory because the latter does not include the additional axiom in (3). Rothbard is trying to claim that (1) entails (2) in some form of verbal logic.
Why do we accept (3)? Not because we deduce it, but because it reflects how our minds work. In our conceptual schema, actions involve things like the instruments used to do the action and the time it takes to do the action. We know how our minds work from experience and introspection, so we accept (3) as an operational assumption, and (2) as a deduction. There is no theoretical insight here, just a recognition that our mind has a conceptual representation of the world which it organizes into categories associated with properties.
Our notion of actions includes categories like actor, thing acted upon, instruments, intentions, time, etc. Our notion of physical objects also includes categories, like color, form, and time and location of existence. It is a trivial observation, not a theoretical insight, that physical objects which exist have color, form, persist through time and obey the laws of physics.
Rothbard’s reasoning continues, in the same vein. The irrationality demonstrated in this article is mostly harmless, because the conclusions are correct, and do not imply bad policy. The real harm with praxeology comes when its proponents present pernicious economic nonsense as though it were logically deduced, using Rothbard’s harmless cognitive nonsense as a justification for failing to demonstrate the logic.
