By comparison with the physical sciences psychologists tend to pay little attention to ontology. This has had unfortunate consequences. Contemporary trends suggest a dual ontology, with psychology rooted in neurophysiology and social conversation. The notion of a ‘conversational skill’ bridges the two basic categories of psychological reality. The use of causal concepts in writing up psychological research is to be avoided since it enshrines a misunderstanding of the kind of necessity that is important in the normative control of social activity including conversing. Classical psychological experimental methodology needs radical revision since it is not appropriate to the investigation of collective semiotic structures. These points are illustrated with examples from recent empirical work by social constructivist psychologists.