Let us look at scientific inquiry as “an ocean, continuous everywhere and without a break or division,” in Leibniz's words (1690/1951, p. 73). Hans Reichenbach nonetheless divided this ocean into two great seas, the context of discovery and the context of justification. Philosophers, logicians, and mathematicians claimed justification as a part of their territory and dismissed the context of discovery as none of their business, or even as “irrelevant to the logical analysis of scientific knowledge” (Popper, 1959, p. 31). Their sun shines over one part of the ocean and has enlightened us about matters of justification, but the other part of the ocean still remains in a mystical darkness where imagination and intuition reign, or so it is claimed. Popper, Braithwaite, and others ceded the dark part of the ocean to psychology and, perhaps, sociology; but few psychologists have fished in these waters. Most did not dare or care.

In this chapter, I will argue that discovery can be understood by heuristics (not a logic) of discovery. I will propose a heuristic of discovery that makes use of methods of justification, thereby attempting to bridge the artificial distinction between the two. Furthermore, I will attempt to demonstrate that this discovery heuristic may not only be of interest for an a posteriori understanding of theory development, but also may be useful for understanding limitations of present-day theories and research programs and for the further development of alternatives and new possibilities.