# Can you prove a scientific theory is true?

I've heard many scientists claim that science is not based upon assumptions we believe are true, but upon factual truths found empirically via the scientific method.

For example, they claim the fact that light travels at a definite speed in a vacuum (the same in all inertial frames of reference) is "true". But how do you actually prove that something is true beyond being a true proposition in all experiments performed about the speed of light?

Is this not having the whole thing backwards? I expect that if the speed of light is indeed finite and invariant, and this is a truth that goes beyond any experiment, then I'm going to find that the speed of light is invariant in any experiment. I should not, however, infer that there is an absolute truth because I can confirm a statement is true in a finite number of experiments.

If light always travels at c in a vacuum, I can confirm it in my experiment. A positive truth value of the implication should not be able to tell anything about the sufficient statement, unless we are able to prove that the sufficient is true also whenever the implication is true (which would turn the statement into an "if and only if" type of proposition).

One could say the exact same about Newtonian mechanics. They are not said to be "true" anymore, at least not with the same frequency I hear the statement about the speed of light is true.

So, can a scientific theory (for example, Special Relativity) be proven true? Or can it only be proven false? And as always, do my own claims and questions make sense at all?

• Possible duplicate of Is Science about Truth or Adequate Models? Aug 22 '18 at 21:27
• Why should science be falsifiable? is another duplicate. This issue is also not specific to science and depends on definition of "prove". Strictly speaking, we can not even prove that the Sun will rise tomorrow. We can only be confident to various degrees and the possibility of being wrong is always there, with anything. Aug 22 '18 at 21:33
• What value do you ascribe to "truth"? What theory of truth do you presuppose? In pragmatic sense a scientific theory indeed can be true. And it seems to me that confirmed science in itself having pragmatic value should be called pragmatically true as it serves its function. Aug 22 '18 at 23:05
• I am just a beginner in the field of philosophy in general, let alone epistemology. In my mind, the word "truth" means something that is always, under any circumstance, verified about the universe (even if there's nobody to perceive such a thing). For example, "either it's raining or it is not", as much as being a tautology, it is such a truth. The statement "given Zorn's lemma, the well-ordering theorem follows" is also true in this sense (yes, that might lead us down a dark alley) because the two are equivalent things. Aug 22 '18 at 23:32
• This question is just the question of scientific realism isn't it? At least replacing "prove" with the more liberal "justify". Scientific realists claim that our best theories are true, and that we are justified in thinking so (by induction and abduction), while anti-realists don't make this claim. Aug 23 '18 at 7:22

Can you prove a scientific theory is true?

No, you cannot. Scientific theories generally provide some sort of generalized description of observed related phenomena. The theory of General Relativity for example delivers an excellent (as in amazingly accurate) mathematical description of how gravity works (outside of the quantum scale), which has corretly predicted a large number of astronomical observations and which can explain a lot of observed phenomena.

However, since we can only make a finite amount of observations, we must assume that there may be circumstances in which the theory does not hold.

The conclusion would then be that while we cannot ultimately prove General Relativity to be true, we can (in principle) prove it to be false by discovering a reproducible effect that contradicts GRs predictions.

The point I am trying to make here was made first by Karl Popper, whose works "The Logic of Scientific Discovery" and "Conjectures and Refutations" are the cornerstones of what is called "Critical Rationalism".

Apologies for just linking to wikipedia. I'm sure there are better sources out there, but the wiki articles, in particular the 3rd one, should at least give you a rough idea about what I mean.

What it means for a scientific theory to be "proven" is different from what it means for a mathematical theorem to be proven. Indeed, for any scientific theory, we can never be 100% sure that there aren't somehow some unusual conditions under which it is not accurate, and under which we have done no experiments yet. This was the case for Newtonian mechanics. Of course, we can become extremely confident that the theory will make accurate predictions, at least under certain conditions. This link ("Scientific Proof Is A Myth") has more discussion.

• I could only accept one answer, but I had a hard time choosing between yours and Flo's. Aug 23 '18 at 9:42
• More precisely, the problem is not that the theory is wrong. It is rather than the theory relies on assumptions which are wrong. In a world where such assumptions hold, the theory would of course be correct. Jan 16 '19 at 16:00

Yes you can.

"I should not, however, infer that there is an absolute truth because I can confirm a statement is true in a finite number of experiments."

This "absolute truth" is irrelevant because reality is inductive. There is no "absolute" perception that humans have so it's not misleading to call something as truth when we used the strongest form of reasoning that we use for every other aspect of our lives. The quality of this truth based on the number of observations is a different topic though.

• In the absence of a perception of absolute truth, how do we know that a scientific law is proven? Aug 22 '18 at 18:07
• Would you deny absolute truths exist such as all triangles have 3 sides? We can distinguish temporal truths and permanent truths. So the point the OP seems to Express is why is truth used in an absolute sense when scientist really mean temporal truths. If you mean temporal truths then Express that publicly. Some truths are subjective and those are temporal. Aug 22 '18 at 18:42
• @Logikal “all triangles have three sides” is a case of circular reasoning, since a triangle is defined to have three sides. Are there any (probably) absolute truths that are not circular? Aug 22 '18 at 21:12
• @David Thornley probably in the same way that I can predict your mind will have no uncertainty of your immediate death if I offer you a cup of methylmercury, cyanide, or methanol despite a test has never and will likely never be conducted given your exact body composition. So unless you are curious in having a sip then we can agree that you think chemistry principles from theory and expeirment are proven.
– Cell
Aug 22 '18 at 21:16
• @Logikal No I don't deny the absolute truth that triangles have 3 sides, but triangles don't exist so it's not relevant here.
– Cell
Aug 22 '18 at 21:18