Science does not rest on metaphysical assumptions

It’s a commonly made claim: science depends on making metaphysical assumptions. Here the claim is being made by Kevin Mitchell, a neuroscientist and author of the book Innate: How the Wiring of Our Brains Shapes Who We Are (which I recommend).

His Twitter thread was in response to an article by Richard Dawkins in The Spectator:

Dawkins’s writing style does seem to divide opinion, though personally I liked the piece and consider Dawkins to be more astute on the nature of science than he is given credit for. Mitchell’s central criticism is that Dawkins fails to recognise that science must rest on metaphysics:

This is a “foundational” view of science, supposing that we build knowledge from the bottom up, and that the foundation consists of axioms of logic, mathematics and metaphysics. This idea runs into a huge problem: how do we validate metaphysics? Everyone has given up on the quest for a priori truths. And if we can’t validate metaphysics, then how can we argue that science arrives at truth if it rests on unwarranted assumptions?

I regard the foundational view of epistemology as wrong. Instead, we should adopt the view that philosophers of science call the Quinean Web view, also described, prior to Quine, by the analogy of Neurath’s raft.

This says that science arrives at a model of the world that consists of an intertwined web of ideas. We validate and improve the web by comparing the resulting world model to reality. But none of the individual ideas is “foundational” in the sense that it is axiomatic and not open to testing or challenge. Any and all ideas within the web can be assessed, and either accepted or rejected, by evaluating how well they help the overall web to model reality.

Crucially, this testing and verification extends to all parts of the web, to the logic, the mathematics, and to any “metaphysical assumptions” that you consider science to be making.

In Neurath’s raft analogy, any part of the raft can be replaced while standing on the other parts of the raft. Of course one cannot replace everything simultaneously (you’d have nowhere to stand) but one can assess what each and every part contributes to the ensemble by swapping it in and out.

We know that science arrives at sufficiently-true models of reality because it works. That is, if we use science to engineer a bridge across a gorge, then we can indeed drive a truck across it. And when aerospace engineers use science to design and build aircraft, the aircraft do fly. When we use science to design iPhones, the iPhones work. When we use science to predict eclipses, the predictions come true. When scientists develop vaccines, the vaccines work and greatly reduce disease.

The aeroplane would only fly, the bridge would only hold, if we had a sufficiently good understanding of aerodynamics, and of the nature of forces, and of the stresses and strains on materials — and a vast number of other ideas within science and engineering (where “engineering” is the application of science to real-world problems). Everyone accepts that engineering is validated and verified by the end-product working as designed.

But, just as much, the fact that the aeroplane flies also validates the mathematics used to make the calculations, and the logic underpinning all the reasoning used throughout. If “2 + 2 = 4” or modus ponens were not true (meaning, were not good models of how the world actually is) then the science and engineering that employ such tools would fail.

And the same applies to any “metaphysical assumptions”. Either: (1) such metaphysical assumptions make no difference to the predicted times of eclipses, or to the load bearing of the bridge, or to the function of iPhones, or the calculations of quantum mechanics — in which case science does therefore not depend on assuming them, or: (2) such metaphysical assumptions do make a real-world difference to the verifiable predictions of science — in which case these “assumptions” are tested and verified along with the other ideas in the overall web whenever we test scientific models against reality.

And that latter would mean that the “metaphysical assumptions” are not metaphysical at all, they are themselves scientific ideas that model reality, and are just as testable as all the other parts of scientific models.

The Quinean web understanding of science tells us that there is no good reason to make any fundamental epistemological distinction between the “scientific” ideas within the web and the “mathematical”, “logical”, and “philosophical” ideas. Such labels might be useful for different areas of knowlege (in the same way that labels such as “biology” and “chemistry” are useful), but there is not a big epistemological divide between them.

At this point, someone might be tempted to respond: but doesn’t this analysis all depend on the Quinean-web view of science being true, and surely that’s a philosophical claim, so how do you verify that?

But, again, ideas about the nature of science and how science works — along with any other relevant issue of philosophy — is just another set of ideas that is intertwined with the rest of the web of ideas with which science models the world. And the Quinean-web view is verified in the same way as any other scientific idea: it amounts to the best explanation that we have.

This is not a foundational view of epistemology, it’s a boot-strapping account of epistemology, and it’s the only one that properly explains why science is so successful in modelling the world.

If you really think that: (1) science rests on metaphysical assumptions; and that (2) these assumptions cannot be verified and so are likely wrong; and that (3) if they are wrong, then scientific ideas will not be true, then what’s your explanation for the fact that astronomers’ predictions of eclipse times do come true, that bridges carry traffic, and that iPhones work?

22 thoughts on “Science does not rest on metaphysical assumptions

  1. Dan Dana

    Coel, I always enjoy your blog posts.

    You might notice your fingerprints on some of my science haiku quintets in my recent e-book, below.  It is dedicated to Bertrand Russell.  Take a look.  I would welcome your comments.




    Science and Secularism:

    Haiku Quintets and Other Musings

    An e-book from Five Palms Press

    From: coelsblog Reply-To: coelsblog Date: Tuesday, December 29, 2020 at 9:37 AM To: Subject: [New post] Science does not rest on metaphysical assumptions

    Coel posted: “It’s a commonly made claim: science depends on making metaphysical assumptions. Here the claim is being made by Kevin Mitchell, a neuroscientist and author of the book Innate: How the Wiring of Our Brains Shapes Who We Are (which I recommend). His Tw”

  2. Neil Rickert

    I agree with you, that science does not rest on metaphysics.

    That said, I disagree with you about the referenced Dawkins article. I’m guessing that Dawkins would see me as one of the people who questions whether there is such a thing as truth.

    Actually, Dawkins implicitly questions it himself, when he says “I hold the view that scientific truth is of this commonsense kind, although the methods of science may depart from common sense and its truths may even offend it.” That’s a view of science as based on pragmatism rather than on truth.

    1. Coel Post author

      Hi Neil,
      Are you disputing that there is such a thing as truth, or merely saying that we can never be sure that science’s models are 100.000% securely true? If (as I suspect) you mean the latter, then you’re likely pretty much in line with Dawkins. As you say, he seems to be taking a pragmatic view that some things are sufficiently secure that it becomes perverse not to regard them as “true” even if there is some remote possibility of everyone being wrong. Abraham Lincoln being dead and the Earth being round and not flat would be examples. Dawkins’s piece was certainly not written in the language that philosophers of science would use (deliberately so, it’s pitched at a general audience), but I don’t think he is asserting that science’s models in general give us 100.0000%-certainty truth.

    2. Neil Rickert

      Are you disputing that there is such a thing as truth, or merely saying that we can never be sure that science’s models are 100.000% securely true?

      I see truth as a property of statements, not as a thing in itself.

      Are models 100% securely true? To me, that question does not make sense. We have no standards by which we can judge whether a model is true or false. We can only judge how well it works as a model. And that’s the basic pragmatism of science.

      Once we have a model, then that model sets up standards for judging the truth of statements within that model.

      Put differently, truth isn’t something out there. We make truth, and our scientific modeling is part of how we make truth.

  3. Paul Braterman

    I don’t know if you share my dislike of the expression “the scientific method”. One may as well talk about “the artistic method” or “the engineering method”, but that’s a side issue.

    We do expect there to be regularities in the universe, and some would claim that that is a metaphysical assumption. But I think your analysis applies. Our expectation is validated up to a point by observation. Of course our firm expectation that this will still be true tomorrow cannot be tested until tomorrow comes, but such expectation has always worked in the past…

    I would go further than you here. I think that the expectation that the future will be like the past is hardwired into our brains, and into the brains of any organism capable of learning from experience. And if it were not true, our brains would never have evolved.

    Notice that this is the very opposite of Alvin Plantinga’s notorious argument that scientific thinking could not be the result of evolution by natural selection. I would maintain that that is exactly how our thinking did in fact evolve, and that its notorious shortcomings, such as jumping to conclusions, seeing connections that don’t exist, attributing motive and agency, and deference for authority, derive precisely from the circumstances within which it evolved.

    1. Coel Post author

      Hi Paul,
      Yes, agreed. I never did understand why Plantinga makes that argument. Natural selection is continually moulding animal brains (and thus the way they think) to fit their environment. It seems to me obvious that that means that the ways an animal brain thinks will end up being a sufficiently good model of how the world does actually work.

      Of course that model may be a “folk physics”, and we won’t have encountered very fast speeds or things vastly smaller than us, so relativity and quantum mechanics will be counter-intuitive and hard to fathom, but it will still be a pretty-good, functional model of the environment we evolved in, and so it will be to quite an extent “true”.

      There will be exceptions, for example it may be true that over-estimating one’s attractiveness to the opposite sex is a selected-for trait, but it will be true to a large extent.

  4. richardwein

    To someone who claims that science requires “metaphysical assumptions”, I would ask, “Why only science and not everyday knowledge?” If they say, “Yes, everyday knowledge requires metaphysical assumptions too”, I would ask, “Children and animals have knowledge, so you’re saying that they make metaphysical assumptions too?”

    We (and animals) learn about the world around us primarily because we are born with the cognitive faculties to do so. Those faculties develop further during our lifetimes, but most of the time (all the time for animals) our cognitive faculties just operate on auto-pilot without our thinking about it or making assumptions.

    That said, the term “make assumptions” is quite broad and vague. In the broadest sense it could be applied to any inclination for our cognitive systems to work one way rather than another. In that sense, animals “make assumptions” too. But I wouldn’t accept for a moment that it’s appropriate to call those “metaphysical” assumptions.

    Years ago I wrote these two blog posts on this subject that may be of interest:

    1. Coel Post author

      Agreed, our brains make “default assumptions” because they work in a particular way, and they work in a particular way because they have evolved to do so, because working that way worked (“worked” in the sense of promoting survival and reproduction).

  5. Brent Meeker

    I agree. I have an idea similar to Quine’s a I call the virtuous circle of explanation. It says that epistemology involves a circular chain of explanation, which is a crude form goes something like this:
    This can be refined and expanded. I call it “virtuous” because in principle it can be expanded to include all knowledge. The point is that an explanation of something you don’t understand must follow a chain of theories to something you do understand.

    As for truth, didn’t Church prove that true is an undefinable property. In any case I think some propositions are true, but there is no “Truth”. The true propositions aren’t a set.

    1. Coel Post author

      I agree with your “circular chain” idea. Another way of putting it is that science is a continual iteration, adjusting the Quinean web to better fit reality, then testing it against reality, then adjusting again, in an ongoing iteration. We do need this sort of circular/iterative/boot-strapping account of epistemology, as opposed to a foundational one.

  6. vampyricon

    When I first read the title, I was sure I would disagree, but funnily enough I agree with most of what you’ve said.

    That said, I think the metaphysics don’t matter stance has its problems, like when it runs into last-Thursdayism. Sure, last-Thursdayism is untestable, but that means the sensible understanding of events is also untestable, when compared with last-Thursdayism. We need another rule that says “Don’t be ridiculous. Of course the universe wasn’t created wholesale last Thursday!” Often this boils down to Occam’s razor.

    1. Coel Post author

      I largely agree, though adopting Occam’s razor to excise such models can be regarded as justifiably scientific (and not just “metaphysical”). Last-Thursdayism adds an extra complication to the model but does nothing at all to add any explanatory value to the model. So all we need do is adopt Occam’s razor as part of the Quinean web, and that is again justified because it works in leading to models that work.

    2. Neil Rickert

      I see last-Thursdayism as one of the reason to take the view that metaphysics doesn’t matter.

      Yes, I’m fine with your “Don’t be ridiculous” rule. But that rule is an example pragmatism. You don’t get to that rule with logic and truth. You get to it by being pragmatic.

      Using logic and truth, there is no argument against last-Thursdayism. Being pragmatic allows us to say that it is absurd. That allows us to declare last-Thursdayism as false. But so declaring amounts to adopting pragmatic social conventions as part of our basis for truth and as our basis for making sense of the past.

  7. Pingback: Does quantum indeterminism defeat reductionism? | coelsblog

    1. Coel Post author

      Your existence a priori is an axiomatic foundation of further discovery.

      It’s a starting point, yes, but not an unquestionable axiom. We can evaluate and question the idea, just as we can with any other idea within the Quinean web.

    1. Paul Braterman

      Your existence is not an assumed axiom of your thinking, but a precondition for its occurrence. Or, as Russell put it, existence is not a predicate. So your most recent comment is correct and *for that very reason* your earlier one is mistaken

    2. Coel Post author

      In order to evaluate and question anything, you have to first exist.

      But there’s nothing to stop you then pondering on what “you” are and in what sense you “exist”. There is no axiom that cannot be questioned (e.g. one can ponder brain-in-vat scenarios).

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