‘Experiment is the sole judge of scientific “truth”,’ declared the physicist Richard Feynman. Ever since the Enlightenment science has been based on the idea that its theories are testable. But now many argue our grandest scientific theories, from string theory to multiverse theory, have no experimental evidence and some claim they are even in principle untestable.
Should we conclude that these theories are not science at all but mere fictional speculation? Or is it enough for a theory to be beautifully coherent and helpful in simplifying our understanding? Then again, is the very idea of experimental proof itself mistaken, since the results are unavoidably interpreted in the light of the theory they are seeking to verify?