Positioning positivism, critical realism and social constructionism in the health sciences: a philosophical orientation This article starts by considering the differences within the positivist tradition and then it moves on to compare two of the most prominent schools of postpositivism, namely critical realism and social constructionism. Critical realists hold, with positivism, that knowledge should be positively applied, but reject the positivist method for doing this, arguing that causal explanations have to be based not on empirical regularities but on references to unobservable structures. Social constructionists take a different approach to postpositivism and endorse a relativist rejection of truth and hold that the task of research is to foster a scepticism that undermines any positive truth claim made. It is argued that social constructionism is a contradictory position.

Secondary prevention programmes for Coronary Heart Disease (CHD) aim to reduce cardiovascular risks and promote health in people with heart disease. Though programmes have been associated with health improvements in study populations, access to programmes remains low, and quality and effectiveness is highly variable. Current guidelines propose significant modifications to programmes, but existing research provides little insight into why programme effectiveness varies so much. Drawing on a critical realist approach, this article argues that current research has been based on an impoverished ontology, which has elements of positivism, does not explore the social determinants of health or the effects on outcomes of salient contextual factors, and thereby fails to account for programme variations. Alternative constructivist approaches are also weak and lacking in clinical credibility. An alternative critical realist approach is proposed that draws on the merits of subjectivist and objectivist approaches but also reflects the complex interplay between individual, programme-related, socio-cultural and organizational factors that influence health outcomes in open systems. This approach embraces measurement of objective effectiveness but also examines the mechanisms, organizational and contextual-related factors causing these outcomes. Finally, a practical example of how a critical realist approach can guide research into secondary prevention programmes is provided.

In this article is it argued that critical realism has two mutually exclusive definitions of ontology. Ontology is defined as both a fallible interpretation of reality and as a definitive definition of a reality beyond our knowledge claims. A slippage in meaning occurs from the former to the latter, as critical realists try to justify the claim that their ontology ought to supply the terms of reference for all scientific research. Rather than defend an alternative ontology, it is argued that ontology needs to be defined in terms of fallible interpretations of social reality. This necessitates the revision and replacement of ontological theories in the course of an ongoing critical dialogue about reality, and precludes the use of one fixed ontology to supply the terms of reference for the sciences. 2

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Critical realists argue that the condition of possibility of the sciences is that they are based on a correct set of ontological assumptions or definitions. The task of philosophy is to underlabor for the sciences, by ensuring that the explanations developed are congruent with the ontological condition of possibility of the sciences. This requires critical realists to justify their claims about ontology and, to do this, they turn to ontological assumptions that are held to obtain in natural scientific knowledge and social agents’ lay knowledge. A number of problems with this approach are discussed and a problem-solving alternative is advocated.