What can philosophers say about scientific discovery? Many logical empiricists had a simple answer: Nothing. According to Popper, for example, philosophers can illuminate the epistemology of testing, but they can say nothing of substance about how scientists generate the ideas to be tested (Popper 1959). Such “A-ha!” moments of creativity are in the province of psychology, not philosophy. Reichenbach distinguished the context of discovery from the context of justification (the “context distinction”) (Reichenbach 1938; but see the entry on   Hans Reichenbach for an alternate  interpretation of this distinction). The process of scientific discovery was thus largely off limits to philosophers.