By "paradigm shift", I mean a certain amount of unlearning, overturning previously established beliefs -- the fixity of species ion the case of evolution, absolute simultaneity in the case of relativity, determinism in the case of quantum mechanics.

ETA:

You are not merely allowed but required to assign a very low prior, in the range of "bloody ridiculous", to propositions which contradict all your available information, or require some massively complex rationalization to be compatible with all your available information.

Note the contradicitions to "available information" listed above.