This paper examines the doctrine of ‘constructivism’ as presented by Ernst von Glasersfeld (1989). Part I attempts to elicit a clearer statement of the concepts, positions and arguments for the latter than is immediately available in the paper. Part II discusses the problem of intersubjectivity in constructivism. The general conclusions drawn from these sections is that the basic concepts and theses of constructivism are, mostly, at best very obscure, that there is very little argument involved, and that where there is it is quite unsatisfactory. Part III ventures an explanation of at least some of the weaknesses in the doctrine, this involving a brief independent treatment of some relevant epistemological questions.

The paper examines central parts of the first of two papers in this journal by Peter Slezak criticising ’sociology of scientific knowledge‘ and also considers, independently, some of the main philosophical issues raised by the sociologists of science, in particular David Bloor. The general conclusion is that each account alludes to different and crucial aspects of the nature of knowledge without, severally or jointly, being able to theorise them adequately. The appendix contains epistemological theses central to a more adequate theory of scientific knowledge.