The demarcation of science is discussed in a wider context of differentiating the elements of scientific knowledge from non-scientific or pseudoscientific cognitive fields. The traditional epistéme/doxa approach fails in differentiating the scientific from non-scientific. To resolve the problem of demarcation the arguments of the demarcation relation have to be made explicit. The heuristics of the explication is seen in the concept of the theory of science. It is suggested that the pluralistic character of the contemporary science should not be conceived as a hindrance to solving the problem of demarcation. Further, the specification of the objects of demarcation on both sides of the demarcation relation makes the possibilities as well as limits of demarcation more visible.