The Compatibility of Naturalism and Scientific Realism

Brian Holtz
Mar/Jun 2005

U.T. Austin philosopher Robert Koons writes:

In "The Compatibility of Naturalism and Scientific Realism" (Dec. 2003) , Brian Holtz offers two objections to my argument in "The Incompatibility of Naturalism and Scientific Realism" (in Naturalism: A Critical Appraisal, edited by William Lane Craig and J. P. Moreland, Routledge, 2000).  His responses are: (1) my argument can be deflected by adopting a pragmatic or empiricist "definition" of "truth", and (2) the extra-spatiotemporal cause of the simplicity of the laws need not be God, or any other personal being.  In both cases, Holtz simply misconstrues my argument.

(1) is an imprecise rendering of my central response, which remains:

Koons' fundamental mistake in his paper is to treat our epistemological criteria for truth -- parsimony and possibly other unspecified "quasi-aesthetic considerations" -- as if they were empirical conclusions rather than methodological assumptions.

(2) is perhaps a reference to my separate disagreement with Koons about the sort of causal closure that constitutes the most coherent notion of naturalism.  (Koons says naturalism is about spatio-temporal causal closure, while I say it is best understood as being about causal closure in which intentionality is always reducible to non-intentionality.). However, I never speak of  "the simplicity of the laws" of nature being an effect needing a "cause". On the contrary, the core of my response is that simplicity of true laws is not an effect in need of a "cause", but rather is built into our definition of truth.

As can be seen below, Koons' response seems not to engage my argument that he "mistakes a definitional (or methodoligcal) connection for a causal connection" and that he "assumes we can make parsimony-independent empirical tests for correspondence-truth and then reach the amazing empirical discovery that the true theories always turn out to be the (ceteris paribus) most parsimonious ones. [..] Koons simply does not address the position that simplicity is inseparable from the notion of truth in an irreducible and a prioristic way." 

Koons' response makes only one glancing reference to my central argument:

Holtz admits that simplicity plays an indispensable role in theory choice about the fundamental laws, and that’s enough for my argument to work

The bulk of my paper was an attempt to demonstrate that Koons' argument depends on the role of simplicity not being "methodological" or "definitional", and in his response all he says on the topic is that we agree that simplicity is "indispensible". This remark simply doesn't address my point: if simplicity is built into the notion of truth, then the simplicity of true laws is not an effect needing a cause -- supernatural or otherwise. My counter-argument is thus that the parsimoniousness of true laws is as much an "effect" as the unmarriedness of bachelors, and that Koons' search for a "cause" here is a category mistake. It would be interesting to know what Koons thinks of this counter-argument, but his response gives no clue.

I define "scientific realism" in such a way that it is incompatible with pragmatic conceptions of truth.

I don't see in Koons' paper a demonstration that scientific realism (as he defines it) is incompatible with the idea that simplicity is built into the proper notion of truth. He quotes Forster and Sober as saying that "viewing simplicity as an irreducible and a prioristic sign of truth" is a "price" for accepting scientific realism, a price paid by "eschew[ing] empiricism". But no explanation is given of what it means to "eschew empiricism" here.  If empiricism is the thesis that all synthetic propositions can only be known from experience, then there is no inconsistency between empiricism and "viewing simplicity as an irreducible and a prioristic sign of truth". (If the empiricism in question here is just the narrow one saying that our criteria for truth constitute an empirical discovery, then the "price" here is just a restatement of what we've bought.)

I define "naturalism" in such a way that the existence of any extra-spatiotemporal cause, whether personal or not, is inconsistent with it.  The word "naturalism" has a large number of possible definitions -- I fastened on one that occurs quite frequently in the philosophical literature (my definition coincides exactly with David M. Armstrong's).  It's my argument -- I get to stipulate what I mean by "naturalism" in the context of my paper. 

As I said: "I agree with Koons that naturalism is the assertion of causal closure, and my disagreement with his characterization of that closure as spatiotemporal is independent of my disagreement with his paper's overall argument. His argument, and my response, is the same for either notion of naturalism."  I have a special interest in the problem of defining supernaturality, and the fact that Koons doesn't here defend his definition from my criticisms of it indeed does not mean that his overall incompatibility argument has been dented. They are separate debates.

I think Holtz goes wrong by supposing that my paper is supposed to be an argument for God's existence, or for the existence of an extra-cosmic designer.

I indeed think that when the causal non-closure Koons seeks to demonstrate is properly analyzed, it turns out to be not spatiotemporal but intentional and thus susceptible to linking with the intentionality of a designer.  But on Koons' spatio-temporal definition of naturalism, it's true that he's only arguing for an extra-cosmic source of simplicity, about which he says nothing more.

As I see it, my argument demolishes a common objection to many theistic arguments: that it makes no sense to look for a cause of the Big Bang, or the laws of physics, or the fundamental constants, because such things could be caused only by something outside spacetime, and this is obviously impossible.

Such an objection can be demolished without construing the simplicity of truth to be an empirical discovery. There are indeed some atheists who have tried to argue that the Big Bang is evidence for an uncaused beginning of the universe, and their arguments are indeed weak. In my judgment, the proper response is to focus not on cause but on explanation, e.g. as Nozick does.

Now, to be fair, there is one part of my argument, a subsidiary part, that Holtz does engage: my claim that if one is a scientific anti-realist (as Holtz is), then one cannot plausibly appeal to the authority/prestige of science to settle any ontological or metaphysical question (such as the existence of God or human souls).  Holtz clearly thinks I'm wrong about this, but I find his argument (if there is one) exceedingly  hard to follow.

Koons seems to have my paper confused with someone else's.  My paper does not mention gods or souls. Also, I don't consider myself a scientific anti-realist.  As far as I can tell, the philosophical debate over scientific realism is plagued by the fallacy of the excluded middle, due mainly to the mistaken notion that there is some sharp and principled distinction between observables and non-observables.

Perhaps this is what's going on: Holtz thinks that there is no such thing as objective reality, and reality that doesn't depend on human practices and preferences (in particular, those a priori preferences that constitute a large part of our theoretical practices). So, science tells us all there is to know about the only "reality" there is.

I do in fact think there is an objective reality, but I also think we lack apodictic certainty in our observations of it. In other words, I believe there is a some defensible middle ground between radical subjectivism and radical realism.

If this is Holtz's view, there are two huge problems with it -- problems that should, I think, persuade any naturalist worth his or her salt that this is not the path to take.  First, there are the powerful arguments developed by the Polish logician Tarski against any pragmatic "definition" of truth. (1) For any sentence S, such as 'snow is white', it is a truism that 'S' is true if and only if S (e.g., 'snow is white' is true if and only if snow is white).  (2) It is logically possible that snow is white, even though it is not useful to believe something expressible by 'snow is white'.  (3) Hence, if 'is true' is logically equivalent to 'expresses something it is useful to believe', then it is logically possible that snow is white even though 'snow is white' is _not_ true. (4) Hence, if a pragmatic definition of truth were correct, it would be logically possible for snow to be white and not to be white (at the same time and in the same way). Contradiction.  (5) Therefore, pragmatic definitions of truth are incorrect.

Koons fails to distinguish between a "pragmatic 'definition' of truth" and a non-pragmatic definition of truth that is chosen pragmatically. I nowhere asserted the position that "'is true' is logically equivalent to 'expresses something it is useful to believe'".  Thus Koons here just does not address my point about utility operating at a meta-theoretic level -- i.e. at the level of choosing one's general-purpose truth criterion, as opposed to the level for deciding particular empirical propositions such as about the whiteness of snow. (This is ironic, since Tarski is famous for demonstrating that truth in a language can only be defined in a meta-language of that language.)  My point was stated thus:

If immediate utility were the way we decided whether individual theories were true, then we might declare true the most baroque or even contradictory theories in an orgy of convenient cognitive dissonance. The criterion of utility in (H) is employed at a more fundamental level, at which we are choosing the fixed truth criterion to apply uniformly to all theories. It might be useful for me to believe particular theses such as I am handsome or funny or well-liked, but I should not do so if I believe at a more fundamental level in the utility of e.g. only adopting beliefs that are parsimoniously consistent with available evidence.

Thus, I don't say "snow is white" is true simply because it is useful to believe that snow is white. Rather, I say it's true because I'm led to that conclusion by my unvarying policy for deciding whether statements are true, and it is this unvarying policy -- not any particular ad hoc truths -- that I adopt for pragmatic reasons.

Holtz will, I assume, want to deny (2), but it is easy to imagine scenarios in which some fact holds, even though it is, all things considered, more useful to believe a sentence expresses the denial of that fact.

What I deny is that it is more useful to an adopt an alternative truth-deciding policy over the usual policy based on parsimonious empirical rationality. However, I can imagine possible worlds in which (for example) gods arrange things so that a policy of revelation-based truth-deciding turns out to be more useful than parsimonious empirical rationality. Luckily, we appear not to live in such a world.

Here again, the pragmatist faces a dilemma. Either his new "definition" of truth is supposed to express a truism, obvious to any competent user of English, or not. The first horn is obviously unacceptable, since many competent English speakers (myself included) find the pragmatic definition far from obvious or undeniable.  So, the pragmatist must claim that his "definition" represents a discovery (a scientific discovery) about the essence of truth.

Koons' dilemma here seems to suffer from an excluded middle.  It's not the case that either 1) the precise semantics of our linguistic constructions must be reducible to "truisms" that are "obvious to any competent user of English", or 2) those constructions embed empirical discoveries about this universe.  For example, 'the present king of France' is a phrase that can be processed by any competent user of English, and yet Bertrand Russell was not doing empirical science when he sharpened our understanding of such phrases with his theory of Definite Descriptions.  Similarly, one could argue that Hilary Putnam added to our understanding of the semantics of the word "water", again without empirical investigation of his Twin Earth. So I don't think it's a stretch to say that a speaker of English can competently process any workaday use of the word 'truth' without necessarily having a fully-developed philosophical theory of truth.

I just don't agree with Koons there is some "essence of truth" about which we can make empirical discoveries (such as the alleged discovery that Truth tends toward beauty or simplicity).  I indeed claim that choosing one's truth criterion is ultimately a matter of empirical pragmatism, even though once it's chosen that criterion (and not pragmatism) is how one decides the truth-value of all particular propositions.  And as I said before:

The "real world" indeed tends to reward one for choosing a worldivew based on parsimonious consistency with evidence (i.e. truth), and tends to punish one for choosing otherwise.  This arrangement is not a coincidence, but it does not suggest a supernatural arranger. Rather, it is entirely to be expected that there be a best practice for thinkers to adopt in thinking about the world and that thinkers under selective pressure tend to adopt that practice.

Koons summarizes:

Thus, the pragmatist must accept at least one case in which the correspondence theory of truth holds: namely, that his definition of truth corresponds with the real essence of truth. He then occupies a self-referentially inconsistent position.

I'm not sure whether Koons here is asserting that there exists a "real essence of truth", or just that his hypothetical pragmatist would have to posit one. I see no reason to posit such a platonic essence. The closest I would come is to remark (as I did) that reality "tends to reward one for choosing a worldivew based on parsimonious consistency with evidence (i.e. truth), and tends to punish one for choosing otherwise."


The second critical problem with Holtz's position is that he gives us no reason for accepting his particular version of the pragmatic definition of truth (one that incorporates scientific standards of parsimony) over any of the myriad of alternatives.

My critique of Koons' argument requires no "particular version of the pragmatic definition of truth" -- it merely requires a recognition that explanatory economy is built into any sensible notion of truth. To deflect my objection, Koons would have to show that no sensible notion of truth can involve explanatory economy in its definition. I presented an extended argument for my position, but Koons makes no direct argument against it.

Koons' phrase "scientific standards of parsimony" suggests a misunderstanding of my position.  Nowhere in my paper do I say that explanatory economy necessarily involves scientific standards.  My position is that explanatory economy is inherent in our notion of truth even outside scientific specialties, and that good science depends on good epistemology, rather than the other way around.

For example, what would be wrong with adopting instead William James's conception of truth, according to which we are free to adopt scientific standards of parsimony when dealing with scientific matters, but free to take into account various "existential" or even emotional considerations when dealing with religious, moral and interpersonal matters? All Holtz can do here is pound his shoe on the table, asserting that James is being "unscientific" (who cares about that?), or insist that a thoroughgoing scientistic attitude is more "useful"

The word "unscientific" does not appear in my paper. I only used the word "scientific" when quoting Koons, and never when describing a conception of truth or standards of parsimony or "attitude".  I do indeed imply that one's truth criterion should be applied to all domains of knowledge, but my complaint (if any) against selective application would be based on inconsistency and selectivity, not unscientific-ness. 

 -- but where's the psychological and sociological evidence for that claim?

Rather than plead guilty to scientism, I'll say again that valid epistemology is the foundation for valid science, rather than the other way around. (Note the irony of Koons invoking psychology and sociology in the prosecution of scientism.)

And what to do about those who adopt radically different conceptions of what "usefulness" consists in, whose "goals" (note Holtz's casual reference to "our goals" on page 4) are radically different from Holtz's? Whose “goals” count? Those of Holtz and his pals? Why should anyone else care about that?

I never said that anyone's goals count more than anyone else's.  For example, if Jane's goals don't include avoiding car accidents, then she is free to ignore what I would call the truths of optics in her use of her car's mirrors while changing lanes.  Each person need only care about her own goals, not mine or those of my pals. My reference to utility and goals was intended not to claim that there are preferred or objective standards of utility, but in fact to short-circuit the potential objection that my theory of truth depends on some particular standard of utility. Rather, my theory applies to anyone who has any utility function whatsoever.

The naturalistic pragmatist will quickly find himself mired in a morass of relativism.

One needn't seek refuge in complete and absolute objectivity in order to steer clear of absolute relativism. The regularities of this universe provide a reliable way of testing one's epistemology (including one's truth criterion), and we are provided (if not mandated) a set of default goals derived from our nature as intelligent social mammals in a universe subject to the second law of thermodynamics. People can exchange those goals for others (perhaps at their own risk), but their actions will inevitably reveal what goals -- and what truth criterion -- they have chosen.

There is another serious mistake in Holtz’s piece, although it is entirely tangential to my argument.  Holtz admits that simplicity plays an indispensable role in theory choice about the fundamental laws, and that’s enough for my argument to work, but he’s wrong in thinking that “simplicity” here means only ontological parsimony.

"Ontological parsimony" -- presumably, parsimony in the number or kinds of entities in one's ontology -- is only one facet of parsimony, and I did not mean to claim it is the only facet. I indeed talk about a "
parsimonious empiricism that provisionally accepts our fundamental natural laws as brute facts while rejecting ontological commitments for which we lack motivating phenomena", but I also say "simplicity, elegance, symmetry, and invariance are all just facets of parsimony (i.e. explanatory economy)."

Holtz, and anyone else interested in the matter, should read Weinberg’s chapter on “Beautiful Theories”. For reasons of brevity, I quoted only Weinberg’s conclusions, but these conclusions are well supported in the book by a half dozen examples from the recent history of physics.

In what Koons labeled as Weinberg's conclusion, Weinberg used variants of the word "beauty" nine times, and otherwise describes this notion only in terms of simplicity and irreducibility.  This seems to be nothing more than explanatory power and economy, and the Weinberg quote ends saying that "we would not accept any theory as final unless it were beautiful".  Thus Weinberg in fact emphasizes that "beauty" -- i.e. simplicity, deductive fecundity, and evidentiary fidelity -- is a methodological assumption built in to "what we mean by an explanation":

We demand a simplicity and rigidity in our principles before we are willing to take them seriously.  Not only is our aesthetic judgment a means to the end of finding scientific explanations and judging their validity -- it is part of what we mean by an explanation. [p149. emphasis in original]

Thus Weinberg seems to agree with me that the criteria that constitute beauty are in fact built into our notion of what counts as truth, rather than being the empirical discoveries about the world that Koons wants them to be.  (Appended below is a detailed examination of Weinberg's "Beautiful Theories" chapter.)

The essential role of aesthetic standards of elegance in physics is quite close to being a commonplace in contemporary history and philosophy of science. You can find it well documented in Kuhn’s The Structure of Scientific Revolutions or, more recently, in Bas van Fraassen’s Laws and Symmetry.

It is indeed a commonplace for physicists to wax poetic about the beauty of the simplest theory that currently fits the evidence. What is rare is an example of a theory enduringly being called both more beautiful and more true despite being surpassed by some other available theory in terms of its explanatory power and economy.  There is no such example in Weinberg.   If Koons could produce such an example from any source, it would resoundingly defeat my objection -- and revolutionize the philosophy of science.

In "Beautiful Theories", Weinberg initially says beauty consists of
"Simplicity" of course is included in explanatory economy.  "Inevitability" here means that the theory consists more of deductions from fundamental principles than it does of ad hoc stipulations -- which again is part of explanatory economy. "Rigidity" here just means the the theory explains the most evidence without being contradicted by any of it -- which again is explanatory power and economy.  (Later Weinberg talks explicitly of "theories that are beautiful because of a rigidity imposed on them by simple underlying principles" [p150].)

Weinberg attempts again to define theoretical beauty as "the beauty of perfect structure, the beauty of everything fitting together, of nothing being changeable, of logical rigidity" [p149].  His "perfect" hyperbole notwithstanding, Weinberg here seems to define beauty as just the property of occupying a peak of explanatory power and economy in the landscape of currently available theories.

Indeed, Weinberg makes some concessions about the significance and efficacy of beauty. He points out that the sense of beauty doesn't always work [p133], and gives examples of its failure in orbital mechanics and genetics. Weinberg explains the origin of the physicist's "sense of beauty" with three factors that make the power of beauty much less mysterious:
Koons cites this last quote in his paper as evidence that the universe is governed by theories that are unreasonably beautiful.  But the answers to fundamental problems are by definition not currently reducible to or derivable from other theories, and this no doubt is a very big part of why those answers tend to be considered beautiful.

Weinberg in fact emphasizes that "beauty" -- i.e. simplicity, deductive fecundity, and evidentiary fidelity -- are methodological assumptions built in to "what we mean by an explanation":

We demand a simplicity and rigidity in our principles before we are willing to take them seriously.  Not only is our aesthetic judgment a means to the end of finding scientific explanations and judging their validity -- it is part of what we mean by an explanation. [p149, emphasis in original]

Thus Weinberg seems to agree with me that the criteria that constitute beauty are in fact built into our notion of what counts as truth, rather than being empirical discoveries about the world.  None of Weinberg's examples -- gravitational theory, particle theory, wave mechanics, non-Euclidean geometry, phase transitions -- constitute an example of a theory enduringly being called both more beautiful and more true despite being surpassed by some other available theory in terms of its explanatory power and economy.

Granted, Weinberg does remark on the beauty and surprising utility of mathematics, and he cites Bohr's "possible explanation" that "mathematics has only a limited number of forms that we can adapt to Nature, and it can happen to one that he finds the right forms by formulating entirely wrong concepts". Bohr was more right than Weinberg realizes about why math works. First, the universe contains a lot of discreteness, invariance, and continuity, all of which are mathematical subjects. Second, mathematics is defined and designed to be nothing other than the study of the truths that are the demonstrably necessary consequences in any system of quantity, relation, and inference. So it is unsurprising and natural that mathematics describes the physical universe so well.