According to this meta post, it is community consensus that theoretical answers should be deleted as off-topic. The reasoning is that

[o]ne of the premises of skepticism is the application of the scientific method: empirical proof validates (or disqualifies) theoretical models. All questions we allow here are empirical in nature, thus answering via a purely theoretical model is inappropriate.

Where does an answer start to become "theoretical" in this sense? Obviously, no answer can be "empirical all the way through". Even the application of concepts from everyday language to describe an empirical phenomenon isn't purely empirical, but this is clearly not meant by "theoretical answer".

Perhaps an undisputedly theoretical answer would

  • apply some model on a high level of abstraction
  • that makes a lot of assumptions
  • the model itself and the application are very hard to evaluate by laypeople
  • the scientific community considers the model just as one plausible contestant among many.

The list is just an example for a clearly theoretical answer. The more difficult question is whether there exists a list of criteria that can be used to distinguish theoretical from non-theoretical answers. The list above is not it.

What about questions like this, which asks whether burning 5 pounds of fuel can produce more than 5 pounds of CO2?

The "theoretical" answer comes down to: Yes, when two reactants are combined, the mass is greater than that of one reactant only. The argument is very basic, it does not even require an understanding of chemistry beyond knowing that "burning" has something to do with "adding" oxygen. But more importantly, there is no empirical study on this question that we could cite, because it would be too trivial to be scientifically useful. (It might be useful as a primary or middle school experiment.)

Any answer to this question can only be theoretical, if the "theoretical answer" yardstick is too narrow. Lacking "empirical" references, there could be no acceptable answer, which is a pity because it's not a bad question.

Of course, an answer could cite some textbook that explains the basics of chemical reactions, but applying these basics to the question at hand would still be considered "theoretical". That's nonsense!

So how could a tentative yardstick for "theoretical" answers look like?

  • That particular question is not a great example, and you are not representing it correctly. It's not whether the gas produced can be more than the fuel, which is trivial to answer by reference (the definition of combustion should suffice to answer). The question is that whether a particular complex fuel (gasoline) produces a specific amount of a gas (carbon dioxide), which requires non trivial calculations.
    – Sklivvz
    Jan 26, 2018 at 11:26
  • 2
    @Sklivvz The question was posed thus: "How is it possible for 5-10 pounds (2.3—4.6 kg) of liquid to produce 20 pounds (9 kg) of gas?" That sounds like it could easily be answerable by the definition of combustion, indeed. But would that be a theoretical answer? Jan 26, 2018 at 12:28
  • the question is literally titled "Are 19.6 pounds of CO2 produced from burning a gallon of gasoline?"
    – Sklivvz
    Jan 26, 2018 at 14:52
  • 1
    @Sklivvz and yet the question body literally asks ""How is it possible for 5-10 pounds (2.3—4.6 kg) of liquid to produce 20 pounds (9 kg) of gas?" Jan 26, 2018 at 14:55
  • And what is your point? All answers are answering the title, not the body, so you are posting a blatant strawman argument.
    – Sklivvz
    Jan 26, 2018 at 14:58
  • 2
    @Sklivvz Actually, I'm not trying to argue anything. I'm just interested in the border that delineates a "theoretical answer" (deemed unacceptable and deletion-worthy) from a skeptical/empirical answer (acceptable and on-topic). This is regardless of the example. The example is instructive to the extent that it can be answered with a quite trivial application of very basic "theory". This application is (almost) equally simple for the question in the title and the body. Indeed, the non-deleted answer performs this simple two-step application. Jan 26, 2018 at 15:16
  • You draw the border at "requires additional references" on one side and "that's absurd" on the other, the mods sometimes just decide what questions and answers they don't like and pick a reason to delete them.
    – daniel
    Feb 2, 2018 at 10:54

2 Answers 2


The way the scientific method is presented in the excerpt you quoted is a travesty. It sounds like what a high school student would say after learning about it in class. If a model has been validated time and again by experiments, you don't need to rerun a whole experiment to test out every single computation you make. If I throw my computer out the window, it will fall with a 9.8 m/s2 acceleration, and I will be able to compute the duration of the fall using basic algebra and a yard stick. I don't need to run an experiment specifically for this computer, specifically for my window, specifically on this day with this wind speed. Just like I don't need to look up an authority source or run the experiment myself to perform the basic algebra necessary to compute how much CO2 burning a gallon of gasoline would produce. There's nothing "unscientific" about that.

It is also especially contradictory that on a website proclaimed to be for "skeptics", an answer from an official source is the only one acceptable, whereas one that can be checked by anyone with middle school level knowledge of chemistry is not acceptable.

I understand not wanting to be confused by cranks pretending to be experts and drowning the reader in high-tech mumbo jumbo. But some common sense has to be applied. Mindlessly following a rule to the letter makes no sense if it has such evidently inane consequences in special cases. If something can be checked by a high school student with a calculator, it's nowhere near "theoretical" enough to be harmful.

  • The fact that the 7 deleted answers could not agree once on how much CO2 was produced does not matter? That there at least 4 different models used (contradicting each other)? That even the "high quality" answers did not address the question at all, confusing gasoline with octane? In other words. should we drop any vestige of quality here to appease the ego of 7 people?
    – Sklivvz
    Jan 26, 2018 at 14:57
  • And complaining that the different models gave approximate answers that don't happen to be exactly equal? Are you serious?
    – user31438
    Jan 26, 2018 at 15:41
  • 1) leave personal attacks at home, I have been very patient with your bad attitude, but it's time to start being constructive now 2) the answers don't claim to be approximate to that point. (5 is not 8, sorry).
    – Sklivvz
    Jan 26, 2018 at 17:55

There is not a consensus for the accepted answer to that FAQ. Indeed at present a third of the votes on that particular answer are downvotes

This can also be seen by the fact that an alternative view was expressed in another answer to that meta-question, that alternative view was upvoted, and then was deleted (apparently challenging the claimed consensus was deemed off-topic) to prevent it getting more support. Comments on the question and answer were also deleted, with the ironic effect of suggesting that a consensus about prohibiting theoretical answers existed when the empirical evidence was that it was being challenged

The recent activity related to the mass of CO2 produced from burning gasoline, including seven deleted answers, one of which 34 upvotes - more than double the policy leading to its deletion - also shows that the policy does not have a consensus. A numerical analysis of the chemistry involved is actually more convincing when considering a claim by the US Energy Information Administration than quoting a statement by the US Department of Energy

A substantial number of people on this site do not see skepticism as essentially being references to fact checking by others and then appeals to authority of those fact checkers to state a single objective truth. The Royal Society's motto nullius in verba (take nobody's word for it) is closer to what skepticism and this site ought to be

If cranks post bad answers to questions, they are likely to receive negative comments and be voted down, as they are on other stackexchange sites. Deleting every answer bar one, and most of the commentary, is the antithesis of skepticism

  • I'm sorry but you are mixing up the FAQ with the policy. The policy has been there, in various forms from the beginning. The FAQ was my attempt at documenting what the policy was.
    – Sklivvz
    Jan 26, 2018 at 14:54
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    @Sklivvz: I fundamentally disagree with you, and apparently you with me. I think your comment on another meta-answer "Find a reputable reference, such as an expert in the field performing the same calculation, then report their findings" reflects what I object to. And I am not the only one
    – Henry
    Jan 26, 2018 at 15:02
  • I don't have a problem with our disagreement, only with confusing a FAQ for a policy discussion, that's all.
    – Sklivvz
    Jan 26, 2018 at 17:56

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