Discovering Complexity: Decomposition and Localization as Strategies in Scientific Research

Introduction

INTRODUCTION In Chapter 1 we emphasized that our investigation is directed at identifying the cognitive constraints affecting theory development, and in Chapter 2 we introduced decomposition and localization as the central heuristics figuring in our treatment of the development of mechanistic explanations. We turn now to developing a more detailed analysis, one grounded in historical analyses, of how scientists actually develop mechanistic models. As we proceed, we will focus on choice-points, points at which decisions are made that shape the explanatory endeavor. The decisions scientists make are affected by their own cognitive characteristics (for example, the fact that they are agents with bounded rationality); theoretical considerations that suggest that one or another sort of explanation might be viable for the particular problem; and available empirical data. In this part we will identify some of the initial choice-points that are confronted before actually developing an explanation that would qualify as fully mechanistic. These focus on the identification of discrete systems in nature, the assignment of activities to them, and the determination of whether these systems can be functionally decomposed. Before it is possible, or even relevant, to develop a fully mechanistic explanation of how a system performs some function-and, therefore, before the heuristics of decomposition and localization are properly brought into play-it is necessary to identify what functions are preformed and what system performs these functions. We speak of this as isolating the locus ofcontrol. A locus ofcontrol is not necessarily a system that operates in isolation; rather it is one that carries out a transformation of inputs into outputs that is what constitutes realizing a specific function. Although such an identification of a locus of control is critical to any attempt to develop a mechanistic explanation, claims to have identified such loci are often controversial. We start in Chapter 3 with a discussion of two domains in which controversy is still alive. One involves identifying the locus of control for behavior . The other involves the locus ofcontrol in evolution. In each case there are prominent scientific traditions placing control in the environment. Radical behaviorists argue that organisms are not loci of control for behavior -that such control lies outside the organism. Likewise, the Darwinian explanation of evolutionary adaptations looks to the forces ofselection operating on individuals ofthe species, rather than to factors internal to such individuals. Each of these positions can be placed in counterpoint to another which sees the system as, in an important sense, serving as a locus of control. Cognitive psychology, as a recent mentalist turn, rejects the 36 . II. Emerging Mechanisms claim that one can understand behavior without looking inside the organism , and so treats the cognitive system itself as the locus of control. A similar argument has been made in the case of evolutionary theory. This is particularly true of Haeckers and other orthogenetic programs in the nineteenth century, which view evolution as an internally directed process leading to increasingly complicated forms of organization. There are other cases in which such controversies have been resolved. One was the nineteenth-century controversy over the locus of control for respiration. Although experimental evidence was marshaled, this alone was not sufficient to settle on tissue cells as the locus of respiration. Theoretical issues, including a variety of questions such as the role the tissues actually play in living organisms and the factors determining the rate of respiration, were also important. Bernard and Ludwig offered essentially theoretical arguments which they took to show the role of the blood in respiration. These were countered by Pfluger, who offered a convincing account of how the cells figure in respiration and how they are able to control the rate of respiration. In section 4 we explore how Pfluger was able to bring this controversy to an end and establish the tissue cells as the locus of respiratory phenomena. Determining the locus of control is the first critical choice-point in the development ofthe mechanistic program. The cases we examine in Chapter 3 show some of the arguments that figure in controversies over this issue. As will be true of additional choice-points explored in subsequent chapters, one seldom has definitive evidence for the decision one makes; to some extent it will be made on the basis of other factors. Yet the choice is critical, for it determines the course of subsequent research. If one rejects some proposed locus of control, the task becomes one of identifying an appropriate alternative source of control-a challenge still confronting those who...