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S16j. When is a theory confirmed?
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Any deviation from a law can only be 'confirmed' by narrowing error 
bars for the parameters modeling the deviation. As long as the error 
bars contain zero, the law counts as confirmed.

With time, confirmation of the law may be at a higher level of 
accuracy, or (as in the case of neutron masses) confirmation of the 
deviation (if the more accurate error bars no longer contain zero).

If one disputes any of the established theories because of not enough 
confirmation, one can as well dispute Lorentz symmetry, translation 
invariance, zero photon mass, general relativity, etc., which are 
basic to contemporary physics but all confirmed only to a certain 
precision.

There are experiments testing the limits of all these assumptions, 
but even when one of these experiments succeeds (as in the case of 
neutron masses), the previous theory remains valid to the accuracy
it was known to be valid before. In this sense, older theories don't
die even when they are superseded. A well-known case is Newton's
gravitational theory which is still taught and heavily used 
although not completely correct.