I have noticed a type of fallacious reasoning that conflates truth and success. For example, a company might assume their predictive models are correct because these models make the company more money. However, turns out this was a conflation of success and truth; those models were incorrect. A few years later, the models will collapse or make incorrect predictions and it will be revealed that they were based on shoddy or untrue principles all along. The fact the system predicts the outcome does not imply the system is based on the true principles underlying the system.

There are other cases this fallacy in history. Genghis Khan, for example, sent letters (e.g. to the Shah of Bukhara) arguing that his lightning-fast conquests were proof that his Mongol forces were blessed or guided by God. The Muslims made the same argument after they conquered an area almost the size of the Roman Empire in two centuries. Countless groups argue that their success, growth, or size is proof of their validity or even religious truth.

Another example is in science. Ptolemy's model of astronomy explained the motion of the heavens by assuming each planet moved on a sphere called an epicycle (see full explanation). It also placed the Earth at the center of the solar system. Its predictive success was unsurpassed until Copernicus, and it is still used by planetarium projectors to model the solar system. However, we now know it is a woefully inaccurate description of the universe. In retrospect, it seems clearly fallacious to conclude the Ptolemaic model is true because it was successful.

Do you agree that arguments of this form are fallacious? Does this fallacy have a name?

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    The truth is what works. Some make it a definition, so it is not considered a fallacy. You could say it is affirming the consequent (if A is true then it would work, A works, so A is true), but abductive inference in science has the same form. Formal validity is not a proper standard for informal reasoning. – Conifold Feb 4 at 6:03
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    It falls under 'Correlation is not causation', which manifests as a number of different named fallacies: post hoc ergo propter hoc, false cause, converse argument, and others. The fact a system predicts the outcome does not imply the outcome is caused by the principles underlying the system. The former is only correlation. Ptolemaic epicycles of celestial spheres worked well, but they don't exist. To assert causation, you also need a model based in an accepted paradigmatic background and a mechanism with separately verifiable steps. And that just makes this credible, not proven. – jobermark Feb 4 at 21:43
  • @jobermark Excellent reasoning. The Ptolemaic example is perfect, exactly the case I should've mentioned! I added it to my answer. A model's predictive success does not reflect that the model has any access to the actual truth. – Jeremy Hadfield Feb 4 at 23:34
  • I've actually noticed quite often people conflating financial success with virtue or intelligence. – Bread Feb 5 at 2:26

The fallacy you're hinting can be characterized broadly as the false cause fallacy. Britannica defines the fallacy as follows:

The fallacy of false cause (non causa pro causa) mislocates the cause of one phenomenon in another that is only seemingly related.

That being said, the question you ask is quite interesting. While I agree the proposition

P: If X is successful in regards to a certain goal, then X is necessarily true

is quite strong and suspect, the weaker probabilistic form of the proposition isn't as problematic (as with many propositions which are framed in terms of probability), which is

'P: If X is successful in regards to a certain goal, then X is probably true

In fact, many scientific realists actually use a form of the above weaker premise to argue for scientific realism. The Standford Encylopedia of Philosophy states:

The most powerful intuition motivating [scientific] realism is an old idea, commonly referred to in recent discussions as the “miracle argument” or “no miracles argument”, after Putnam’s (1975a: 73) claim that realism “is the only philosophy that doesn’t make the success of science a miracle”. The argument begins with the widely accepted premise that our best theories are extraordinarily successful: they facilitate empirical predictions, retrodictions, and explanations of the subject matters of scientific investigation, often marked by astounding accuracy and intricate causal manipulations of the relevant phenomena. What explains this success? One explanation, favored by realists, is that our best theories are true (or approximately true, or correctly describe a mind-independent world of entities, laws, etc.). Indeed, if these theories were far from the truth, so the argument goes, the fact that they are so successful would be miraculous. And given the choice between a straightforward explanation of success and a miraculous explanation, clearly one should prefer the non-miraculous explanation, viz. that our best theories are approximately true (etc.).

(emphasis mine)

Obviously, there are objections which are raised to the so-called "miracle argument" (see the linked article). It should also be noted that while 'P could be plausibly argued for in a scientific domain, in other domains (such as a business) it may not apply as well. Nevertheless, I think it is clear that the falsity of 'P (the weaker form of P) is not so obvious that it would rise to the level of an informal fallacy.

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    Excellent answer! Sensible with good references, and added new insight to my question. I agree with 'P, your inductive/probabilistic restructuring of the fallacy. My problem was with P, which is clearly fallacious but doesn't seem to have a formal name as a fallacy. – Jeremy Hadfield Feb 4 at 6:50
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    @ChristianDean Welcome to the site, and thanks for being open to constructive criticism :) I often edit my own posts many times, quite often because I've learned new things from the comments. – Chris Sunami Feb 4 at 15:36
  • @ChristianDean Thanks for the edit, I have rescinded my downvote. – Chris Sunami Feb 4 at 17:43

This is the fallacy of questionable cause, one of the best known, and most common informal fallacies. It is closely related to affirming the consequent which is a formal fallacy where a statement of the form "If X then Y" is misinterpreted as implying "If Y then X." You often hear this warned against with the statement "correlation does not imply causation," meaning that just because two things occur together, it does not imply that one causes the other. As with all informal fallacies, it takes its strength from its similarities to a stronger argument. With properly designed and controlled experiments, it is indeed sometimes possible to infer a cause from an effect.

Questionable Cause: Concluding that one thing caused another, simply because they are regularly associated.

My initial intuition is that the religious case is different --but is it really? This is still a "questionable" cause in the religious case. We can't definitively call it false --it might be true --but we can judge that the evidence falls short of the claim. (It's not fallacious, however, to say that the evidence is "consistent with" the claim.) It's important to note, however, that the weakness of the argument does not, in itself, provide evidence AGAINST the claim. Even if Khan is wrong (about his victories proving his religion), that does not prove his religion is wrong as well.

It's worth noting that the Bible does address this specific dilemma directly. The Old Testament reports several instances where the adherents of different religions are challenged to perform the same miracle under the same circumstances. This is essentially a controlled experiment where the variable being tested is what religion is being invoked. (Also of interest: Jesus's statement that "Good fruit comes from good trees; bad fruit from bad trees" --but that's a whole other discussion).

  • Good point. Although this may not be the origin of the fallacious reasoning. We don't know the Truth in any absolute sense, and so we don't know whether truth and success have been correlated in the past. Some people who use the fallacy I described may simply assuming truth --> success because they have been regularly associated in the past. But this isn't the most common form of the fallacy - I doubt most people conclude success is based in truth because they've seen lots of instances in the past where success was caused by truth. They're not basing fallacious reasoning on past correlations. – Jeremy Hadfield Feb 4 at 18:02
  • I think invoking "Truth" here is misleading. What the company actually observes is that when they use their method, they make money. This is not necessarily a "false" cause because their method might actually be working, but it is a "questionable" cause because they haven't adequately demonstrated that their method is the thing making the difference. // It might not be ever possible to prove with 100% surety that their method is working via the mechanism they propose, but with properly designed experiments, it becomes possible to make a "strong argument" that the method is a genuine cause. – Chris Sunami Feb 4 at 18:13
  • That makes sense. With careful analysis we can determine with reasonable certainty that our models are "accurate" and "true," and not just "successful" in a myopic sense. But what about the case of my religious examples? E.g. I don't know if we can use careful experiments figure out whether Genghis Khan's or Islam's success in history were because these groups had the "true religion." I don't think the fallacy of questionable cause applies in those cases. I'm looking for a way to label & dissect the fallacious logic of this oft-cited connection between truth and success. – Jeremy Hadfield Feb 4 at 19:25
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    Right. Don't want to commit the fallacy fallacy here (assuming e.g. that because the Khan's reasoning is fallacious, he must be incorrect). It does seem like a somewhat fringe case of the fallacy of questionable cause or the more strongly worded false cause fallacy. That becomes clear once we make the implicit reasoning of the claim (success ~= truth) more explicit and clear. Thanks for your answer & the discussion! – Jeremy Hadfield Feb 4 at 19:51
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    It was an interesting question to consider :) I've edited my answer to include direct consideration of the religious aspects. – Chris Sunami Feb 4 at 19:55

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