Social constructionists believe that experimental evidence plays a minimal role in the production of scientific knowledge, while rationalists such as myself believe that experimental evidence is crucial in it. As one historical example in support of the rationalist position, I trace in some detail the theoretical and experimental research that led to our understanding of beta decay, from Enrico Fermi’s pioneering theory of 1934 to George Sudarshan and Robert Marshak’s and Richard Feynman and Murray Gell-Mann’s suggestion in 1957 and (...) 1958, respectively, of the V–A theory of weak interactions. This is not a history of an unbroken string of successes, but one that includes incorrect experimental results, incorrect experiment-theory comparisons, and faulty theoretical analyses. Nevertheless, we shall see that the constraints that Nature imposed made the V–A theory an almost inevitable outcome of this theoretical and experimental research. (shrink)