The theory is based on a philosophical approach to causation, the theory of powerful particulars (Harre and Madden 1975; Madden and Humber 1974), and I shall begin with a brief sketch of that.
THE THEORY OF POWERFUL PARTICULARS
The central concept in the philosophical theory proposed by Harre and Madden (1975) is the 'powerful particular'. This is a thing (such as a physical object or a person) with a certain type of property; namely, a power to produce certain sorts of effects. 'Causation always involves a material particular which produces or generates something' (Harre and Madden 1975: 5). Harre and Madden rejected the traditional association of power in philosophy with animism and anthropomorphism, and argued that the causal powers of things are based on the 'chemical, physical, or genetic natures of the entities involved' (p. 5).