  A second, quite different, sense of ‘priority’ in which evidence has sometimes been held to be prior to theory is that of semantic priority. According to this view, the meanings of hypotheses that involve ‘theoretical terms’ (e.g., ‘electron’) depend upon the connections between such hypotheses and that which would count as evidence for their truth—typically on such accounts, the observations that would confirm them. The view that (observational) evidence is semantically prior to theories was central to the logical positivist conception of science. On this picture, meaning flows upward from the level of observation; a given theory is imbued with whatever meaning it has in virtue of standing in certain relations to the observational level, which constitutes the original locus of meaning. The picture was gradually abandoned, however, in the face of repeated failures to carry through the kind of theoretical reductions that the picture seemed to demand, as well as appreciation of the point, forcefully emphasized by  Putnam[28]  and others, that the meanings of theoretical terms do not seem to change as our views about what counts as confirming evidence for hypotheses in which they occur evolve.