Firstly, to be clear, I'm not trying to say that science is all nonsense or not useful or anything of the sort, since that's obviously not the case. If nothing else, it's incredibly useful for making accurate predictions about any number of phenomena.

However, it does seem to me that, to consider a scientific theory true (as opposed to just being useful) because it correctly predicts things about the physical world and has reasonable explanatory power is an example of the fallacy of the converse. Something like: if theory a is true, predictions x, y, and z must be correct predictions about the physical world. The predictions are correct, therefore a is true. That's a clear example of assuming the consequent, which is a common fallacy.
And yet, it surely can't really be so simple as that, because if it were then surely scientific realism would have been long since entirely rejected. So what am I missing that makes scientific realism reasonable?

There's Occam's razor of course, that a good theory should make as few assumptions as possible, and that, given the choice between two theories that both make the same predictions, the theory with fewer assumptions/independent parameters should be preferred. But that doesn't say anything about if multiple theories have the same number of independent parameters AND make the same predictions. Plus, while it's certainly true that, all else equal, if theory a makes assumptions A, B, and C and theory b makes those same assumptions but also assumes D, theory a is more likely, simply because P(A and B and C) ≥ P(A and B and C and D), just making fewer assumptions doesn't necessarily make a theory more plausible, since the specific assumptions made might themselves be implausible. Afterall, it's not necessarily true that P(A and B and C) ≥ P(D and E and F and G), even assuming statistical independence. And, finally, even if theory a is more likely to be right, that's not a guarantee it's right.

Basically, I just don't see how it's reasonable to think we could ever even know whether our theories are at least close to the truth or if we just keep making models that most closely fit the data we currently have but don't describe how the world actually is. What arguments does scientific realism make to refute these problems?

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    Occam's razor has no implications about truth whatsoever. Commented Apr 22, 2023 at 0:03
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    Who says scientific theories are "true"? What would "true" mean for a scientific theory?
    – Frank
    Commented Apr 22, 2023 at 0:11
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    As for accuracy, isn't that another question? For example, if the theory of special relativity is more accurate than classical gravity, and that is observable in GPS corrections, wouldn't you say that special relativity is more accurate than classical gravity at least in some range of the parameters? Doesn't it seem like we could know that for certain?
    – Frank
    Commented Apr 22, 2023 at 0:16

4 Answers 4


Most of our normal thinking about the world is not purely deductive. When you wish to judge which is a better location for your papercraft business, or where you put your hat, or who is the current Prime Minister of the United Kingdom, or really anything about the state of the world, you cannot entirely rely on deductive logic. These things must always rely on heuristic reasoning and association of patterns.

This means that, technically, all your reasoning about these subjects is invalid and committing formal fallacies. Should you stop doing it, then? Well - you could not function as a person if you stopped such reasoning.

Scientific realism is only another example of applying heuristics to reason about the physical world, rather than pure deductive reasoning.

  • "I remember the news saying Rishi Sunak is the current Prime Minister of the United Kingdom. Therefore, Rishi Sunak is the current Prime Minister of the United Kingdom." (logically fallacious; your memory could be mistaken, the news could have been mistaken, there could have been a sudden change in PM since you read that news.)
  • "I remember textbooks stating the outcome of experiments designed to determine the properties of atoms, such as Rutherford's gold foil experiment. Therefore, objects are made out of atoms with the observed properties." (logically fallacious for similar reasons as the PM inference is fallacious.)

These statements are both fallacious, and if you reject the second one then consistency would demand you also reject the first one, i.e. refuse to assert that Rishi Sunak is the current PM of the UK. If you take this position you would have to refuse to assert the truth of any facts at all about the empirical world. This would make it inconvenient to hold a conversation, at least.

I think a more palatable view is to interpret statements such as, "I assert X," "I believe X," and in some contexts "X is true," as a shorthand for "I am highly confident of X," with the precise level of confidence somewhat ambiguous. So we may say that Rishi Sunak is the PM of the UK, meaning by this only that we are confident of it based on heuristic evidence, though there is a chance we could be wrong. And it is in the same spirit that we can say that a paper airplane is made of atoms, and other claims of scientific realism.

  • Bayesian probability shifts to, what odds you would bet on given statements, & so is open to whatever heuristics calculations models and other methods, you reasonably think will help you win your bets..
    – CriglCragl
    Commented Apr 22, 2023 at 10:51

The Stanford Encyclopedia entry on Scientific Realism states that Scientific Realism "recommends belief in both observable and unobservable aspects of the world described by the sciences." That is quite a bit weaker than claiming to know that scientific theories are true, and arguably your argument doesn't imply that belief shouldn't be recommended. (You may read more of the entry to get more of a flavour of what scientific realists claim and what they don't claim.)

Looking at comments I add that under the label of "scientific realism" one can indeed find quite strong commitments to the truth of the scientific theories, however I don't think that anyone seriously would be a scientific realist just based on the logical fallacy pointed out in the question. It is well known that more arguments are needed (a major one being Putnam's "no miracles" argument, i.e., that explaining the extraordinary success of many scientific theories by other means than those theories being at least approximately true would amount to believing in miracles), and ultimately, as far as I'm aware, scientific realism is never sold as a "true" result of deductive logic.

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    This doesn't quite seem right to me. From the same source: "Amidst these differences, however, a general recipe for realism is widely shared: our best scientific theories give true or approximately true descriptions of observable and unobservable aspects of a mind-independent world." This includes some element of a commitment to the actual success of scientific epistemology, in addition to the possibility of such success. The Approximation allows for some degree of uncertainty, but nonetheless proposes that at least some scientific claims are confirmed by scientific method.
    – Paul Ross
    Commented Apr 22, 2023 at 1:50
  • +1 The reply is short and might be misconstrued upon the turn of phrase claiming to know, but I think the emphasis by traditional epistemological phrasing that to know is to be some sort of unqualified certain* seems consistent with the intent.
    – J D
    Commented Apr 22, 2023 at 2:56

Here is the point I believe you are missing.

The overall science program is not a curve-fitting exercise, in which the scientist adjusts the coefficients (i.e., free parameters) in an equation (s)he has cooked up so as to more closely match experimental data.

Instead, the model/equation is assembled from scratch (i.e., from first principles) using very general properties like energy conservation, time-reversal symmetry, Lorentz invariance, etc. which in combination place strict limits upon the form that any model or description of phenomena are allowed to take, if it is intended to correctly describe the universe we inhabit.

That model is then used to make experimentally testable predictions about outcomes. If the predictions are wrong (Mother Nature always bats last!), then the model is either missing an important component or one of the foundational principles which were assumed in formulating the model were in fact inapplicable.


Let me offer a broader, interdisciplinary view of the deeper underlying issue here:

Yes, the fallacy here is to imply science recognizes such a thing as something being absolutely “true” (or ”false” for that matter). When the whole point of science is that there is no such thing, and the point is usefulness: All we have, is statistically significant observations giving us useful predictions for getting closer to our (arbitrary/instinctual/emotional) goals. But this mindset of an absolute reality existing outside of our minds, is heavily spread by many people even in the “scientific” field, who should know better. You have given a harmful definition of “science”, essentially.

This is a problem that Sabine Hossenfelder (German physicist known for “cutting through the bullsh*t”) and Harald Lesch (German physics and philosophy professor) have addressed many times: There seems to be a lot of “science” that is not actually science and misses the entire point, in favor of some actually religious notions of absolute reality, absolute truth, and such things. Which were born out of the ancient religious notion of there being a “soul”, and that “soul” somehow existing separately from the body and our physical reality. You can spot this pattern easily, because people defending it will always put a heavy emphasis on their beliefs, while merely repeating the statements… instead of using observations and valid logic to reason about them.
An example is “It’s NEVER aliens!”. When in reality, it’s neither not aliens nor is it aliens. It’s the third option: “We don’t know”. It’s useless! We can’t act on the information / there is not enough information. Saying that just because we can’t tell it’s aliens it MUST be not aliens, is just as unscientific as the converse. As (in these cases) we can’t tell that it’s not aliens either. It’s just useless. Which means you cannot act as if it was the case, but it also means you cannot act as if it was not the case. It’s just irrelevant for your life. As you can imagine, this leads to a lot of unnecessary conflict with other religious people aswell. Just replace “aliens” with “god” in the above paragraphs, and observe. :) … In actuality, a scientist would accept and defend reliable observation of a “god”. It’s just that that has never been given to them by anyone. It’s just one of many creation myths. The “big bang” being the favorite one of those treating science as a religion.

To be frank, both philosophy and mathematics have these religious and scientific branches to them. (E.g. people who believe reality itself emerges from math and math’s “proofs” being superior to that of physics, instead of math only gaining its validity from statistically reliable observations of the predictions of its axioms in the first place. [Hence Gödel’s incompleteness theorem being a thing.])

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