One central problem with which philosophy of science has traditionally been concerned is that of the (normative) appraisal of those theories which lay claim to ‘scientific’ status. Can we specify universally applicable conditions which one theory has to satisfy in order to be a better scientific theory than another? (The demarcation problem, which is now associated with Popper's name, and which is the problem of whether we can specify the conditions a theory must satisfy to be scientific at all, is a sort of ‘zero case’ of this problem.) The generalized demarcation problem is, it seems to me, the primary problem of philosophy of science. There are three major traditions in the approach to this one problem. [The aim of this paper is to sketch these three traditions and to investigate their strengths and weaknesses.]

THREE MAIN SCHOOLS OF THOUGHT CONCERNING THE NORMATIVE PROBLEM OF APPRAISING SCIENTIFIC THEORIES

Scepticism

One school of thought on the appraisal problem can be traced back to the Greek tradition of Pyrrhonian scepticism, and is now known as ‘cultural relativism’. Scepticism regards scientific theories as just one family of beliefs which rank equal, epistemologically, with the thousands of other families of beliefs. One belief-system is no more ‘right’ than any other belief-system; although some have more might than others. There may be changes in belief-systems but no progress. This school of thought, temporarily muted by the stunning success of Newtonian science, is today regaining momentum particularly in the anti-scientific circles of the New Left; its most original and colourful version is Feyerabend's ‘epistemological anarchism’. According to Feyerabend, philosophy of science is a perfectly legitimate activity; it may even influence science.