Methodological Individualism

Why methodological individualism? 325reduction’ is ‘that one theory can in principle do all the explanatory work ofanother’. 4 In the further development of the doctrine of reduction, however,suggestions have been made to use this term in a broader sense, to cover alsocases which are not eliminations. 5Two kinds of reduction are commonly recognised: (1) Philosophical or epistemologicalreduction, which proceeds by the definition of the (non-logical) terms ofone language by the terms of another language. The typical requirement ofepistemological reduction is that the terms of the reducing language denote entitiesthat are primary relative to the entities denoted by the terms of the reducedlanguage. (2) Scientific reduction, which proceeds by the deduction or derivationof one theory (or science) from another theory or (science). 6 Epistemologicalreduction has been treated in chapter 6 ( pp. 168–78). In this section our concernis scientific reduction.Kenneth Schaffner distinguishes four approaches to scientific reduction. Theyare: (1) the Nagel-Woodger-Quine paradigm; (2) the Kemeny–Oppenheimparadigm; (3) the Popper–Feyerabend–Kuhn paradigm; and (4) the Suppesparadigm (Schaffner, 1967:138f). Of these, the Suppes paradigm may beomitted, since, according to Schaffner, it can be shown to be a weaker form ofthe Woodger–Nagel–Quine paradigm (the Nagel paradigm, for short), ‘in fact soweak as it stands that it will not do as an adequate reduction paradigm’(Schaffner, 1967: 145).Of the various approaches to reduction, Ernest Nagel’s is undoubtedly themost influential. Virtually all subsequent discussions about reduction take theirpoint of departure in this approach. According to Nagel, reduction is formally arelation of logical entailment between two theories (or sciences). One theory, thesecondary, is said to be reduced if it can be deduced or derived from another,primary, theory (Nagel, 1949: 119; 1961: 352). Nagel distinguishes two types ofreduction. Homogenous reduction, where the primary and secondary theories (orsciences) are about the same type of phenomena, and where the secondarytheory (or science) employs only such descriptive terms as occur also in theprimary theory (or science), and with approximately the same meaning. Typicalfor homogenous reduction is that the primary theory is more general than thesecondary theory and includes the latter as a special case, valid within certainboundary conditions. An example of a homogenous reduction is the explanationof Galileo’s laws for freely falling bodies – which apply to the boundary conditionsobtaining at the surface of the earth – by Newtonian mechanics. Thesecond type is heterogeneous reduction, where the primary and secondary theories(or sciences) are of qualitatively different kinds, and where the secondary theory(or science) employs descriptive terms, not to be found in the primary theory (orscience). The most important case of heterogeneous reduction is microreduction,where the primary theory (or science) refers to entities and processeswhich are parts of the entities and processes referred to by the secondary theory(or science). Nagel’s primary concern is with heterogeneous reduction (1949:102–4; 1961: 338–42).For reduction to be possible, certain formal conditions must be fulfilled. In the