Carl Saganand the Difference
Between Orthodoxy and Heresy
IN HIS CLASSIC 1959 WORK The Logic of Scientific Discovery, the philosopher of science Karl Popper identified what he called “the problem of demarcation,” that is “the problem of finding a criterion which would enable us to distinguish between the empirical sciences on the one hand, and mathematics and logic as well as ‘metaphysical’ systems on the other.” Most scientists and philosophers use induction as the criterion of demarcation—if one reasons from particular observations or singular statements to universal theories or general conclusions, then one is doing empirical science. Popper's thesis, presumably not derived through induction, is that induction does not actually provide empirical proof (“no matter how many instances of white swans we may have observed, this does not justify the conclusion that all swans are white”) and that, de facto, scientists actually reason deductively—from the universal and general to the singular and particular. 1 But in rejecting induction as the preferred (by others) criterion of demarcation between science and nonscience, Popper was concerned that his emphasis on deduction would lead to an inevitable fuzziness of the boundary line. If a scientific theory can never actually be proven, then is science no different from other disciplines of knowledge?
Popper's ultimate solution to the problem of demarcation was the criterion of falsifiability. Theories are “never empirically verifiable,” but if they are falsifiable then they belong in the domain of empirical science. “In other words: I shall not require of a scientific system that it shall be capable of being singled out, once and for all, in a positive sense; but I shall require that its logical form