 Evolutionary epistemology is open to instrumentalist (Toulmin 1972) and realist (Popper 1972) interpretations (Callebaut and Pinxten 1987; Radnitzky and Bartley 1987). A biological approach to human knowledge naturally gives emphasis to the pragmatist view that theories function as instruments of survival. Darwinist evolution in biology is not goal-directed with a fixed forward-looking goal; rather, species adapt themselves to an ever changing environment. In applying this account to the problem of knowledge-seeking, the fitness of a theory can be taken to mean that the theory is accepted by members of the scientific community. But a realist can reinterpret the evolutionary model by taking fitness to mean the truth or truthlikeness of a theory (Niiniluoto 1984).