Scientific falsifiability

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The concept of scientific falsifiability is supposed to be one of the foundations of modern science, and involves scientists doing what Feynmann referred to as "sticking your neck out"

A hypothesis is something which looks as if it might be true and were true, and which is capable of verification or refutation by comparison with facts. The best hypothesis, in the sense of the one most recommending itself to the inquirer, is the one which can be the most readily refuted if it is false. This far outweighs the trifling merit of being likely. For after all, what is a likely hypothesis? It is one which falls in with our preconceived ideas. But these may be wrong. Their errors are just what the scientific man is out gunning for more particularly. But if a hypothesis can quickly and easily be cleared away so as to go toward leaving the field free for the main struggle, this is an immense advantage.
— Charles Sanders Peirce, Principles of Philosophy    

Physical falsifiability

Karl Popper

According to Karl Popper, "... the criterion of the scientific status of a theory is its falsifiability, or refutability, or testability.", where "testability" was emphatically not meant to mean the finding of supporting evidence of argument, but a genuine attempt to falsify the theory in a competent way, with a decent element of danger for the theory concerned. Popper considered the Eddington test to be a genuine test, as the theory's light-bending predictions were outside the range of previous theory, and there was no previous evidence to suggest that the result would actually come out "right". The test of a gymnast's balance was not whether they could walk along a straight line on the floor, but whether they could walk a tightrope 300 feet up in the air with no safety-net. In this sense testing (as attempted falsification) was to be open to similar criteria to the way that judges were supposed to judge whether someone had committed the offence of "attempted murder" under English Law – one was supposed to have a "sporting chance" of success (in murdering the individual or disproving the theory), otherwise it didn't count.

Popper's "falsification" approach was the result of an effort to distinguish between "real science" and pseudoscience (or religion), where proponents could claim that anything and everything was supporting evidence for their beliefs.

This is closely related to the concept of being able to make specific scientific predictions – a theory that can be retrospectively used to predict any outcome has no predictive accuracy - we cannot predict a specific outcome, and test the theory by seeing if it actually comes to pass as predicted (literally, as said beforehand).

Logical falsifiability

Logical falsifiability a matter of using logic to demonstrate that a theory does not work as claimed, or has logical internal inconsistency. When Fred Hoyle argued that his steady-state theory described a stable universe, and Stephen Hawking argued that the solution was inherently unstable (any perturbation, however small, was liable to trigger local collapse or expansion), this was a logical falsification.

Similarly, when it was discovered that special relativity could not coexist in the same system as the general principle of relativity, this was a logical falsification of Einstein's 1916 theory that did not require supporting experimental evidence – the theory did not have a logically consistent way of dealing with experimental evidence.


" We do not know where we are "stupid" until we "stick our neck out," and so the whole idea is to put our neck out. And the only way to find out that we are wrong is to find out what our predictions are. It is absolutely necessary to make constructs."
The Feynman Lectures on physics (
"It is easy to obtain confirmations, or verifications, for nearly every theory — if we look for confirmations."
Karl R. Popper, Science as Falsification 1963 (


GR1916 deserves credit for its falsifiability (proved by the fact that it was falsified!), while GR1960 is a much weaker system.

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