The demarcation problem refers to a dispute in philosophy of science concerning how to distinguish between ‘science’ and ‘non-science’, with the latter category including both pseudoscience and legitimate disciplines which are non-scientific, such as art and literature. Philosophers debating this question have found it surprisingly difficult to arrive at clear, universal criteria for what makes something ‘scientific’.
One difficulty is that there appears to be a continuum between disciples that everyone agrees are clearly scientific, most prominently physics and chemistry, disciplines that are generally regarded as ‘softer sciences’, such as biology or geology, disciples whose status as sciences is disputed, such as economics and psychology, and still other disciples which are rarely regarded as sciences, such as history and sociology.
Drawing upon the successes of physics, some have suggested that sciences must develop mathematical theories that describe a wide range of phenomena. This approach is hampered, however by the fact that many sciences (e.g. much of organic chemistry and many fields of biology) are not highly mathematical, while conversely the discipline of mathematics itself is typically not considered to be a science. Another possible criterion based on the experience of physics could be the use of experiments, but this would entail that a disciplines like astronomy or geology, where experiments are often impossible, would not be counted as sciences.
Yet another popular approach, often associated with the philosopher Karl Popper, is that sciences must make predictions that are falsifiable, meaning that they can at least potentially be proven wrong. If a theory or explanation can never be proven wrong, either because it is too vague or because it is consistent with any possible outcome, then by this criterion it is said to be unfalsifiable and hence unscientific. Although useful as a good rule of thumb, falsificationism has been criticised both for ruling out things that it shouldn’t be excluded, and also for failing to rule out things that should be excluded. In the first case, historians of science have demonstrated how repeatedly throughout history scientists often do not reject hypotheses or theories that are apparently falsified by observation, but instead adapt their theories to account for the phenomena, or posit new causes to explain the discrepancies. For example, irregularities in the orbit of Uranus, which could have been viewed as a ‘falsification’ of Newton’s theory of gravity, instead led astronomers to correctly predict the existence of the hitherto unknown planet of Neptune. In the second case, certain disciples such as palmistry or astrology often make predictions which are, at least in principle, falsifiable, yet nevertheless their insensitivity to the outcome of such tests leads them to be widely considered as pseudoscience. For such reasons, Popper’s theory of falsificationism does not seem to tell the whole story about what makes a field scientific.
Some philosophers of science have responded to the difficulties in resolving the demarcation problem by arguing that science is not really anything ‘special’ at all; rather it is simply part of the more general activity of studying the world by use of careful reasoning and evidence, a view which renders science as essentially continuous with, and not fundamentally different to, history, literature, or even philosophy. Others argue that science does have key distinguishing characteristics, and have articulated various increasingly sophisticated theories as to what property or collection of properties are definitive of science. Despite such lack of agreement, however, some knowledge of the varying perspectives concerning the demarcation problem is valuable in facilitating a more nuanced understanding of science, and in evaluating the merit of particular scientific findings.
Science and pseudo-science: discussion of the philosophical problems of making the distinction from the Stanford Encyclopedia of Philosophy
Karl Popper and demarcation: analysis of Popper’s approach to the demarcation problem from the Stanford Encyclopedia of Philosophy
The demarcation problem: brief video of philosopher John Wilkins discusses the demarcation problem
Demarcation: Popper, Kuhn, and Lakatos: useful set of lecture notes from philosophy course covering various approaches to this problem