On logic and science

31 Aug, 2021 at 15:42 | Posted in Theory of Science & Methodology | 10 Comments

That logic should have been thus successful is an advantage which it owes entirely to its limitations, whereby it is justified in abstracting — indeed, it is under obligation to do so — from all objects of knowledge and their differences, leaving the understanding nothing to deal with save itself and its form. But for reason to enter on the sure path of science is, of course, much more difficult, since it has to deal not with itself alone but also with objects. Logic, therefore, as a propaedeutic, forms, as it were, only the vestibule of the sciences; and when we are concerned with specific modes of knowledge, while logic is indeed presupposed in any critical estimate of them, yet for the actual acquiring of them we have to look to the sciences properly so called, that is, to the objective sciences. 

In mainstream economics, both logic and mathematics are used extensively. And most mainstream economists sure look upon themselves as “twice blessed.”

Is there any scientific ground for that blessedness? None whatsoever!

If scientific progress in economics lies in our ability to tell ‘better and better stories’ one would, of course, expect economics journals being filled with articles supporting the stories with empirical evidence confirming the predictions. However, the journals still show a striking and embarrassing paucity of empirical studies that (try to) substantiate these predictive claims. Equally amazing is how little one has to say about the relationship between the model and real-world target systems. It is as though explicit discussion, argumentation and justification on the subject aren’t considered to be required.

In mathematics, the deductive-axiomatic method has worked just fine. But science is not mathematics. Conflating those two domains of knowledge has been one of the most fundamental mistakes made in modern economics. Applying it to real-world open systems immediately proves it to be excessively narrow and hopelessly irrelevant. Both the confirmatory and explanatory ilk of hypothetico-deductive reasoning fails since there is no way you can relevantly analyse confirmation or explanation as a purely logical relation between hypothesis and evidence or between law-like rules and explananda. In science, we argue and try to substantiate our beliefs and hypotheses with reliable evidence. Propositional and predicate deductive logic, on the other hand, is not about reliability, but the validity of the conclusions given that the premises are true.


  1. Jerry Brown said: “Maybe I’m wrong, but without some sense of logic all you end up with is emotional statements that are more or less impossible to evaluate except perhaps by the intensity with which they are delivered.”
    Since true paradoxes like “this statement is a lie” exist, aren’t all arguments provable due to explosion? Thus logic is really about emphatically and emotionally banning paradoxes, thus sacrificing completeness in describing nature?

    • Not yet. The paradox hasn’t been proven yet. If you can find some proposition A such that you can prove (A and not(A)), then all hell breaks loose, like you say.
      Goedel’s miracle was to construct an A that had the effective meaning (A cannot be proven). Either A can be proven, giving us (A and not(A)) as the next step, or A cannot be proven leaving us with an incomplete system where some true propositions are unprovable. He left it at that.

    • May I submit as evidence a logic agent program, described in http://subbot.org/essays/liar/lie.html , which allows me to prove that “this statement is a lie” is both true and false?
      Can I avoid all hell breaking loose by choosing when I want to use a contradiction to prove something? Can I be a trivialist, choosing my own facts?

  2. I guess ethical or moral statements do not require much logic behind them. Saying it is wrong to kill others for no reason probably doesn’t require much analysis for most. But you can do it anyways if you want, and pretty well, and end up at near the same place.

  3. So, for example, look at Robert Barro’s ‘Ricardian Equivalence’ idea. It’s an idea that I think is ridiculous, but what do I know. The problem with it is the very questionable assumptions it makes about human behavior- not the logic that is used to draw conclusions from those assumptions. That part seems pretty much ok to me.

  4. It just seems so often when you look at things and see that something is unjust and you really want to make it less unjust that logic is often a tool you can use to point out what is wrong.

    • Jerry,

      Just letting you know I can’t respond to your question.

      • Oh well Henry. I guess we were getting a bit off topic there. But what do you think of my comment above or Lars’ post here? I don’t really understand why someone should not use logic when making any argument. Maybe I’m wrong, but without some sense of logic all you end up with is emotional statements that are more or less impossible to evaluate except perhaps by the intensity with which they are delivered.

        Well I’m glad I got the last word and ended by praising your intelligence. But don’t let that get to your head.

      • Jerry,
        “But don’t let that get to your head.”
        I was terribly miffed that you failed to mention how incredibly handsome I am. I guess I’ll eventually get over it. 🙂 And you won’t be seeing me in that other place. Lucky you.
        I would say, if we are talking about the physical sciences, logic, experimentalism and empiricism can go hand in hand. Experiments in the physical sciences have proved to be repeatable – so it can play a part etc.. Logic is a part of formulating hypotheses. It’s crucial. Hypothesis are formulated then tested. What follows is either celebration or reformulation of the hypothesis. That’s the scientific method, as we all know.
        But economics is a different kettle of fish, isn’t it? Experiments and empirical studies don’t repeat too well and the results generally can’t be transported across time and space (as is the case with the physical sciences). So economics is not particularly amenable to the scientific method. All that’s left is model making and formulating hypotheses which can only be unreliably tested.
        I don’t see any problem with model making in economics. There’s really not much else that can be done. Crazy assumptions are fine as long as their limitations are taken account of and the application of their conclusions to reality taken with the appropriate grain of salt. A start has to be made somewhere.
        I don’t think economics can ever be a true science.
        And I would say Lars is too dogmatic about these matters.

        • Political theory can have notations of scientific endeavor, multidisciplinary input, but well funded ideological machinations like the Powell memo in forwarding a goal seeking agenda kind mess with it.

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