Naturalism and anti-realism in the philosophy of science

Question

I was surprised by the lack of easily accessed discussion on overlap of these popular philosophical terms / ideas. Are they more or less orthogonal?

As I understand it, ontological naturalism says we should believe in the reality of only the entities we can discover in science.

I don't think this definition is against the tenor of this slippery phrase, even though it excludes "non eliminative non reductionist ontological naturalism" (as then some real entities "supervene" on the "hypothetically completed empirical sciences"). See Naturalism: A Critical Analysis (2002, Routledge).

Nothing "spooky", anyway.

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I think that some scientific anti-realists disagree with the realists that we should believe

in the existence of unobservable entities literally

Arthur Fine on scientific realism.

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You're welcome to reply with slightly different definitions, though it may confuse.

Answer 1

The problem you will encounter here is that the main overlap between these two areas is science. Science itself, to be blunt, doesn't really care about philosophy very much, and so it doesn't have a stock answer for you. Or rather, it does, but its answer is a disappointing "It doesn't matter whether these phenomena exist, as long as our theories can correctly predict experimental results and observations." With respect to quantum mechanics, this is sometimes described as the "shut up and calculate" school of thought, which has considerable overlap with the Copenhagen interpretation, but is not quite the same thing (partially because nobody seems to agree on exactly what the Copenhagen interpretation means in the first place).

To be more precise about this, science does not (usually) assume ontological naturalism, but instead (usually) makes the far weaker assumption of methodological naturalism, which can be summarized as "supernatural phenomena are impractical or impossible to study scientifically, regardless of whether they exist, so let's not waste our time thinking about them." (Note: Most of that SEP article is actually about a different definition of the term, but there is a paragraph about this meaning being used "[a]mong philosophers of religion.") You'll notice that this is more of a subjective opinion than a real assumption, and so it is difficult to argue with, at least within the scope that science uses it. It can be interpreted as a stronger statement, about the "true form" of the scientific method, but unless you happen to be a Platonist, it's hard to get excited about that.

As for realism vs. anti-realism, as described above, science is in the business of predicting the results of experiments and observations. Whether or not (say) electromagnetic fields exist is not of scientific interest. What matters is whether the electromagnetic force (which we can directly measure) actually has the direction and magnitude that is predicted by theory. The field is simply a means to that end (i.e. it's an essential part of the theory). So does it exist? Science doesn't care, it just wants to know whether the field is a good tool for making predictions about reality. To put it another way, the field is the map, and what we really care about is the territory. The territory may in fact be identical to the map (in the philosophical sense, i.e. following Leibniz's law), or it may not, but until we identify a specific discrepancy between them, science has no objection to continuing to use that map in order to describe the territory. You could say that science is agnostic with respect to realism.

So where does this leave your question? I'll do my best to summarize the positions here, but I would suggest picking one area and asking a more specific question about that, if you want a more precise answer:

• I've explained the scientific view at length above.
• The realist would tell you that all phenomena described by scientific theories actually exist (or at least, that they exist to the extent that science has correctly identified and studied them). The anti-realist would tell you that there is a distinction between theory and reality, that theory is just a "tool" etc.
• Ontological naturalism would say that all phenomena that really exist must in some sense be physical. But that does not necessarily imply that e.g. electromagnetic fields don't exist, because they still exert a physical influence through the electromagnetic force, so they can still be characterized as physical entities, even if they are not directly sensible to the human body. It can be further argued that the human body itself should not be treated as "privileged" and that there is no meaningful difference between the human eye and an electromagnetic sensor (indeed, the human eye actually senses electromagnetic waves in the form of visible light), or any other measurement apparatus that you could hypothetically build.

Answer 2

Short Answer

They are not orthogonal. In the general case, most philosophers of science reject the supernatural as a working principle and then take a position somewhere in the realist-anti-realist spectrum of belief, often having different ontological views on different classes of phenomena. Working scientists as a whole may not even reflect on the realist-instrumentalist debate carried out by professional philosophers of science.

Long Answer

Ontological naturalism is the metaphysical rejection of the supernatural, which might roughly be understood as the belief that all things are part of the universe's temporalspatial extension and causality. That means it is an ontological presumption. Say someone poses to a scientist the idea of a god. To embrace ontological naturalism would be to conclude that any "superbeing" that existed as a "god" would still be subject to the constraints of the universe; that such a superbeing couldn't violate what we understand as science, and that if it did, our science would need to be improved. For instance, if a superbeing landed on earth and defied gravity, working from the presumption of ontological naturalism would require science to figure out how the anti-gravity was accomplished, not presume it is a supernatural occurrence.

Anti-realism which is generally directed at problems with reconciling contradictions between entities and their properties, such as wave-particle duality which says, the reason an electron is both a wave and a particle is that electrons aren't real in the sense a chair is real, but rather, it is a construct of the mind, and hence when we talk about wave functions as real, we are making a category mistake by placing them in the same category as a chair. In extreme forms of anti-realism, like mereological nihilism, even chairs being real is rejected in favor for the view that only configurations-of-atoms-as-chairs exist.

So, they're not orthogonal. One is talking about an aspect of existence, about rejecting natural-supernatural dualism of what exists in favor of naturalism as a monism. "There is NO supernatural. All that exists does so naturally." The other is taking a stance on existence itself. "Electrons DON'T exist physically and maybe chairs too!" Of course, when you take extreme positions of both and try to marry them, you get counter-intuitive philosophies that seem contradictory. It bears worth mentioning that philosophical positions are generally very complicated, book-length or greater sets of claims.

• A Catholic priest who believes in evolution might reject anti-realism and accept natural kinds, but reject the rejection of God. (See religious naturalism.) This would be rejecting strict ontological naturalism, but accepting scientific realism.
• An atheist scientist may believe in hidden variables and reject the Copenhagen interpretation and claim that even wave forms are real. (See scientific realism.) This would be accepting strict ontological naturalism AND scientific realism.
• An agnostic philosopher of science rejects the supernatural, but remains open to the experience of the supernatural, and believes that the mind collaborating with society constructs all knowledge, and so has strong anti-realist tendencies rejecting the existence almost everything in line with rejecting natural kinds. This would tentatively accepting weak naturalism with a possibility of rejecting strict naturalism wholly, and accepting instrumentalism.

Answer 3

I think @Kevin already gave a good answer, but I think some points should better be explained the other way around.

As I understand it, ontological naturalism says we should believe only in the entities we can discover in science. I don't have a problem with it really, though I dislike some sorts of narrative ruptures, and would suggest pre scientific people might be able to identify some parts of the world. But nothing "spooky", yeah.

I think you're confusing something here. "Supernatural" implies that there is something outside or above (super) of nature that isn't constraint by the laws of nature or doesn't or only occasionally interacts with nature.

Now an ontological naturalist believes that there are no such (supernatural) things. Everything that is part of nature is fully and at all times part of nature. So it's about what they believe, not about what they want you to believe (although that might follow from that depending on how missionary people are about their believes).

And as a consequence of being a part of nature, it would need to interact with other objects and subjects in nature which makes it describable through these interactions. Meaning sooner or later natural sciences would need to be able to find a hint of those interactions.

So in that sense there isn't a "pre-scientific" era because any an all perception of interactions happening in the real world would count as "science" in that regard. So science wouldn't really discard old civilization's descriptions of the movement of stars or tremblings of the earth or the night coming early and only lasting for a couple of minutes or whatnot, they would just reject the interpretations of "a god did it", but would try to find an in-universe explanation that doesn't rely on external indescribable forces.

That being said you might also argue that the attribution of these natural phenomena to a person could indicate their erratic and arbitrary nature and thus the difficulty in finding a good ad hoc explanation. Though again the ontological naturalism argues that there has to be an explanation if it is real (otherwise it would be supernatural).

In terms of Kevin's statement of:

"It doesn't matter whether these phenomena exist, as long as our theories can correctly predict experimental results and observations."

Yes and no. It matters a great deal whether things exist and to a degree the ontological naturalism is at the heart of science because as explained here:

"supernatural phenomena are impractical or impossible to study scientifically, regardless of whether they exist, so let's not waste our time thinking about them."

if the ontological naturalism assumptions wouldn't hold then it would be impractical or impossible to study these things and so science would be a waste of time. What doesn't matter is whether supernatural things exist. That is as long as they stay supernatural (outside of the natural world). So as long as a god doesn't interfere with the real world in a measurable sense that god could exist or not exist and it wouldn't bother a scientist (professionally), because they couldn't measure it either way. As soon as that would change and they would be always or even occasionally interfere with reality, that would be different.

However when you're talking about the existence of natural things, their existence matters a whole lot to the scientist, it's not engineering where you just want a thing to do the thing you want it to do. Scientists actually like to understand how things work. So the best tool they have in their belt is to check whether their hypothesis of how things work yield the same result as what the real world does.

Though in terms of realness, that is a necessary requirement but not a sufficient one. So if you're describing the real territory then your description (map) should align with what you measure in the real world, but just because it does, doesn't mean there aren't also 1000 and more other explanations that would work just as good. So the ultimate arbiter for a scientist is how the real world behaves.

So what is real for science are data and experiments, theories are just a tool, a narrative to explain the existing data and to fill the gaps between the data. That some of the filled gaps turn out to be false and so that the theory needs to be updated because of that is not really a failure of the method but fully intended.

Anyway, I think that scientific anti-realists claim that science has absolutely nothing to say on what "exists" without appealing to what we can conceive of as a phenomena. All theoretical unobservable entities that are postulated in science to do not exist.

Well as long as we can't observe it, it might as well not exist. But anti-realism and realism seems to take a stance in arguing that it does or doesn't exist. While the view of science is usually just "not my business, call me when we can measure it".

With respect to quantum mechanics, this is sometimes described as the "shut up and calculate" school of thought, which has considerable overlap with the Copenhagen interpretation

The problem was that at the time science had found a mythical problem for which there was no good answer and so tons of people came out of the woodwork to produce some strange theories which were often pseudo-science, untestable or whatnot and which did more to confuse and produce fringe experts than to give any insight or understanding. So instead the theorists in quantum mechanics were encouraged to rather further the understanding of their own theory and advance that because it was at least producing results that were in agreement with the experiments. Though that isn't necessarily the be all end all of how one should do science.

Now in terms of scientific anti-realism, arguing that electrons and genes aren't real because we can't see them directly... Well again those are theories that explain the data that we can see and fill the gaps that we cannot see and we keep them as long as they do that job and if we find out that they don't work, we look for better explanations.

TL;DR the ontological realist argues that everything is physical, i.e. is interacting physically with it's environment and is thus measurable by science. The anti-realist argues that things that aren't measurable don't exist, while the realist argues that there are real things existing, while the scientist usually requires the ontological realism to be true, makes no statements about the supernatural (professionally) and treats it's theories as useful rather than real. Meaning they are held, as long as they are in agreement with what experiments confirm but rejected once they are not. Which a scientific anti-realist might call instrumentalism. So ontological realism and scientific anti-realism might not be polar opposites, as both make claims about there not being something outside of physical perception. While if you consider it without instrumentalism, they'd be kinda wrong about that.