Reduction, mechanism and all that

by Neil Rickert

Why I am a heretic

The name of this blog recognizes that some of my views are seen by many to be obviously wrong.  An example of this cropped up recently, when I posted a comment on John Wilkins’ blog.  John seemed to think that I was obviously wrong, though another commenter seemed to agree with me.

Evidently the way I look at the issues is very different from the way that John (and many others) look at the same issues.  This post is intended to discuss those differences in viewpoint, as best I understand them.

Part of why we disagree is because we are from different backgrounds.  We both are from Australia.  John is still there, while I migrated to USA some time ago.  Our differences are not in our geographic backgrounds; they are in our intellectual backgrounds.  Specifically, John is a philosopher while I am a mathematician.  To some extent, I’m a philosopher too, as are most humans.  Philosophizing is part of being human.  But, unlike John, I am not a philosopher by training, nor by profession.

That difference in background shows up in our relation to logic.  For philosophers, logic seems to be a core discipline, and many philosophers take logic to be the basis of reasoning.  As a mathematician, I use logic.  Mathematicians are usually assumed to be very logical people (as we are).  However, my relation to logic is different from what seems to be the relation of philosophers to logic.

As best I can tell, some philosophers seem to take logic as metaphysical.  I take it as a useful tool, but it is only one of the tools available to me.  Some philosophers take mathematics to be a branch of logic, which roughly corresponds to logicism as a philosophy of mathematics.  That was the view of Russel and Whitehead, as presented in their Principia.  It was the view of Frege, and probably of Quine.

By contrast, most mathematicians see logic as a branch of mathematics.  Many, self included, see logic as a relatively minor branch of mathematics.  I don’t think this is just a territorial dispute (as in “who owns the territory of logic”).  The way we mathematicians use logic is different from the way that philosophers use it.  Once we have an axiom system, we use logic to explore the consequences of those axioms.  But coming up with axioms systems is itself an important part of mathematics, but seems to be outside the scope of logic.


If everything is logically reducible to physics, then everything is within the scope of what can be achieved using logic, if one starts with a few basic principles of physics.  This is probably why many non-theistic philosophers are committed to reductionism.  Many theistic philosophers, by contrast, are opposed to reductionism.  Presumably, they see a failure of reductionism as leaving room for their deity.  For myself, I’m not sure why such a fuss.  I am skeptical about reductionism, for the evidence does not seem to support it as best I can tell.  But it really doesn’t matter very much to me.  My relation to the world, and how I analyze questions about the world, do not hinge on any assumptions about reductionism.


The issue of what is mechanical was where John Wilkins disagreed with me.  I’m a bit puzzled as to why.  However, I have had this argument before, mostly in discussions about AI.  Many AI proponents want to say that physical implies mechanical, that the Church-Turing thesis is a characterization of mechanism, and that therefore computationalism (the view that the brain is a computer) is true.  By contrast, I am skeptical that everything physical fits what I mean by “mechanical”, I take the Church-Turing thesis to be about computation rather than about mechanism, and I have my doubts about computationalism.

Words don’t really have meanings.  People mean something, and use words to convey that meaning.  But the meaning inheres in the people, not the words.  If people disagree over what a word means, that’s life and no big deal.  If physical implies mechanical, then why not just say “physical” and stop using the word “mechanical”?  So I don’t understand why John felt it so important to say that Curtis is wrong, or that I am wrong, in our use of “mechanical.”  I’m guessing that it comes back to the way that philosophers use logic.  They see “mechanical” as implying tractable to logical analysis, so if I say something is not mechanical, they suspect that I am suggesting that it is not tractable to logical analysis.  They might be right about that.  But since logic is only one of the tools available to me, I am not bothered that logical analysis might sometimes fail.


4 Responses to “Reduction, mechanism and all that”

  1. Thanks for the measured tone, Neil. I should respond in kind.

    I did not think you were obviously wrong. You are wrong in a way that a great many people are wrong. No shame there. My response to you was based on your, as I saw it, parodying reductionism. It is one of those views that is treated more emotively than reasonably, both within and without the philosophical community. I took some years to come to a flat footed reductionism, and I did so reluctantly, but inexorably. I can talk about this later. For now, let me say that to be a reductionist is not to assert, for example, that we must always be able to do the reduction right now, when, say, studying a biological phenomenon or arguing about economics.

    As to “mechanical”, there are numerous uses in play. One is the algorithmic – a machine is a Turing machine. My objection there is that in the physical world there are no Turing machines, just physical systems that can be described as Turing machines for our purposes but which, like the notion of an Ideal Gas, will fail in some cases.

    Another is the push-pull notion: a machine is anything that is more or less rigid and moves some object. This is the “clockwork” notion of a mechanism (it includes springs, of course).

    I was appealing to what I took to be the best modern notion of a machine – the thermodynamic, in which energy is converted to work. You may disagree that is the best sense (which is a philosophical, not a mathematical nor a logical issue), but given the scope of my discussion (ecology and systems) it was the one I thought best to use. What ordinary people have to say about machines no more applies than what ordinary people think about statistics does in a technical discussion.

    The nature of logic is, as you are well aware, highly contested. Arguably it is at the heart of the 20th century analytic tradition in philosophy. For my money I am an evolutionary epistemologist – the rules of inference we have encapsulate past successes. There is nothing much about the universe that leads us to think logic is prior. Of course, as a reductionist I would say that, but I have in mind the sort of Matrix-stye ontologies that are very popular these days (e.g., David Chalmers). Eugene Wigner’s paper is still the best succinct solution so far as I know.

    In terms of ontologies, I think I know there is a physical world, and no ontology that deflates physics is acceptable to me. If you want to argue that the physical world is composed of information (which is logical atomism, by the way – we philosophers have given that one a fair bit of discussion) you have some problems to resolve. However, it is not obviously false. Neither is reductionism and physicalism.



  2. I was appealing to what I took to be the best modern notion of a machine – the thermodynamic, in which energy is converted to work.

    Let’s look at a well known example of a thermodynamic machine, namely the automobile. Combustion occurs in a cylinder (or combustion chamber), and the resulting pressure causes the motion of a piston. Theoretical analysis uses the Carnot engine, which is an idealization of this kind of system.

    In my usage, the term “mechanical” applies to the moving piston and other moving parts, and not to the combustion. The mechanical part is in the conversion of thermal energy to kinetic energy, rather than in the release of chemical energy. Much of thermodynamics is statistical, which makes it seem far removed from being mechanical.

    For my money I am an evolutionary epistemologist – the rules of inference we have encapsulate past successes.

    I am all for an evolutionary epistemology. But by treating the rules of inference as the “genes”, I’d say that you are doing it wrongly. I’m assuming that you are including scientific laws as rules of inference.

    I see scientific laws as analytic (as necessary truths). If so, then they would generally be seen to have no descriptive content. And that, of course, is why they could not mandate behavior of physical objects (another point of disagreement between us). The long chains of inference that we use in mathematics, cannot be relied upon unless the rules of inference are analytic.

    For an evolutionary epistemology, it is the conceptualization that I want to treat as the “genes.” And that’s where logic shows its limitations, for it really requires a full system of concepts before you start. That does not match science, which is creating new concepts as needed, and modifying existing concept when appropriate. When you are creating a new system of concepts, you have some degree of freedom in how you formulate them. And where possible, physicists use those degrees of freedom to formulate a suitable system of concepts that are in a “nice” mathematical relationship with one another. And that is why scientific laws can be analytic, and it is why data, expressed in terms of concepts, is theory laden.

    In terms of ontologies, I think I know there is a physical world, and no ontology that deflates physics is acceptable to me.

    I find ontology to be puzzling. And what is particularly puzzling, is taking it to be metaphysical. I would want ontology to be part of epistemology. That’s what allows conceptualization of reality to be part of an evolutionary epistemology. I don’t think that requires any deflating of physics.


  3. Interestingly, Alfred Lotka, one of the first to apply thermodynamics to organisms, did so because he wanted to get away from the gory details of mechanisms, the intractabilities they involve, and reach a general treatment.

    The blog entry with the relevant quotes is here:



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