Suppose you have two theories explaining data and no other theory is possible such that they are logically exhaustive. You know all there is to know about the data and theories.

Should you, now,

A) Believe in the one more plausible to you and call it a day in an “all out sense”

B) Have a degree of belief in both

  • 3
    You are asking for an opinion. Sep 8, 2023 at 15:09
  • 2
    Furthermore, your question simplifies to: How does one decide? Which is more psychology than philosophy. Sep 8, 2023 at 15:25
  • Perhaps we should look for dictionary entries from the word "deal" to "xylophone".
    – Hudjefa
    Sep 9, 2023 at 3:05
  • Finally, "more plausible" is meaningless. It's like asking which is "more true". Plausibility and probability are not interchangeable words. If two theories are plausible, then the next step is to determine which theory is more probable. Sep 10, 2023 at 2:05
  • what hinges on it?
    – user67675
    Sep 11, 2023 at 1:08

6 Answers 6


If neither are implausible (impossible) then considering one more plausible than the other is having a (differing) degree of belief in both - that is essentially what "plausible" usually means. If you mean how should we act given our beliefs, that is a different question, and it would depend heavily on the context. Being a Bayesian, I am with Hume (B).


If one but not the other is impossible, then A, else if both are possible then B, else C don't believe either of them.


Unless it's the world theory that answers every question, allows for every prediction is always correct and so simple that leaves no room for investigation and isn't just some pseudoscience that does all that in hindsight. In other words unless you've really "finished" science: You're not supposed to "believe" anything.

Like there is no "let's call it a day in science". Both of these theories will have margins of errors, shortcomings and make predictions about the world that you can test.

From a practical point of view, you're likely going to specialize in one of the theories and treat that as the state-of-the-art while the other will be followed by a different research group or will fall out of favor. Like the derived disciplines are likely going to call it a day and work with the theory as if it were true.

But just because you'd be making such a decision does not mean that you're assigning a level of truth to them. Like if there are 2 cups of the exact same ice cream in front of you and both servings are just enough to feel awesome (not too little, not too much) and you end up picking one does that mean that the other is therefore less able to serve the same purpose? No it might be perfectly fine and you might acknowledge that it's perfectly fine even though you didn't pick it. So you neither call it a day nor have a "believe" in both. You're not supposed to believe your theories are true you're supposed to test them and investigate them.


Here is a physics response.

You temporarily choose the more plausible model but you do not "call it a day". instead, you design an experiment to cast light on which model more accurately represents the physics at play, and then perform it.

Now, as to plausibility, here is how that judgement call is made. for each model, you make the following assessments:

  1. Does the model rely on known physics, or does it rely on or invoke some as-yet unknown process?

  2. Does the model accurately account for previously-collected (historical) data i.e., does it provide postdiction?

  3. Does the model contain few foundational assumptions, or lots of them?

  4. Does the model predict the results of an experiment that no one has ever run before, or is it silent on that topic?


The only possible combination of two hypotheses that are logically exclusive are a hypothesis and its corresponding null hypothesis: X has Y kind of influence on Z vs X does not have such an influence. Finding out the degree to which you should believe in each hypothesis on the basis of experimental results is null hypothesis significance testing.

Extrapolate from your hypothesis to an experiment. Do the experiment and let reality tell you how it is. The universe does not owe your intuition answers that your intuition likes.

Gut feelings and questions on SE are not going to get you to a useful command of epistemology. Take an introductory statistics class. It's free. Two hours a night for two weeks and you'll be done. You won't have the answers to all your questions, but you'll have the thinking tools needed to begin investigating them, and the foundations to seek out and employ additional thinking tools.

  • 1
    Statistics doesn’t tell you what to believe. And cut the condescension.
    – user62907
    Sep 8, 2023 at 18:31

The answer is not black and white- it depends upon the circumstances. For instance, recently my central heating boiler refused to light. There were several possible reasons that could have accounted for it, some more plausible than others. It would have been rather foolish of me to rule out all but the most plausible theory. On the other hand, if my neighbour suggested a malevolent pink fairy was preventing the boiler from working, whereas I had found that the oil tank was empty, I would probable discount the former theory entirely and put my faith 100% in the latter.

  • A lot of the divine explanations I have a hard time putting a 0 probability to goes away when it comes to humans. By this I mean that if some meaningful event happens, I don’t presume that some human with special powers did it. I get the psychological instinct to wonder if it’s god. But arguably, a human coming up with some special unknowable power to design something is more likely than a god. Atleast I know humans exist. If I dismiss the human power so easily, why not god?
    – user62907
    Sep 10, 2023 at 9:49
  • And sometimes, it doesn’t even have to be a superpower. Suppose I’m trying to a land a coin I just bought on heads. If I land a coin on heads four straight times, I’m not wondering if the coin is rigged. Without question, the chance of it being rigged is atleast real and higher compared to some divine power helping me out. And yet I’m more likely to wonder or fear the latter than the former.
    – user62907
    Sep 10, 2023 at 9:52

When choosing between two theories, should you believe in the more plausible one? Or have a degree of belief in both?

Neither because it is better to maintain a stance of skepticism than to take things for granted, as per how you have described the scenario, because such prevents the formation of cognitive biases that may hinder an individual's performance relative to his or her environmental demands leading to self-destruction. Let us presume that wisdom is favorable over ignorance if but from being misled or accepting a falsity.

I consider back in 2013 or 2014 I experienced something paranormal/supernatural/what-have-you, whereby I was encountered by either (1) someone who read my mind or (2) did not read my mind, regardless of arguments that minds cannot be factually read because of epistemic limitations. In my mind, I was putting in effort to telepathically communicate with a certain someone. It seemed that said person appeared, but not in the form I expected. I was spooked.

Maybe it was a powerful being who could read minds from a distance. Maybe it was an AI of the Matrix reading my mind. Maybe something else. Technologically, psychic ability would require massive energy for a psychic if but some extremely sophisticated biology or me being hooked up to a machine.

As per me not having a resolve to the problem of the criterion that provides me with knowledge (knowledge as a fact of reality rather than of arbitrariness), no matter how much I analyze the issue, I cannot resolve the data relative to the theories.

Seems this post is better for the Puzzling StackExchange board.

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