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?