A special merit of Professor Feigl's stimulating essay lies in the clarity with which he draws the issue between phenomenalistic and realistic interpretations of science as one concerned entirely with the evaluation of their relative adequacy as analytic reconstructions of empirical knowledge. Responsible and fruitful discussion of these interpretations cannot therefore be a debate over the truth or falsity of scientific theories. For as he carefully notes, the differences between these alternative analyses are not “pragmatic differences” of the ordinary sort, since no differences in regard to any observable consequences that could weigh for or against a scientific theory can be associated with them. Feigl's own rejection of phenomenalism and his espousal of semantic realism must in consequence also be judged in terms of the standard he himself has recognized as alone relevant in this discussion.