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Causal Explanation in Biology: More Than MechanismsCausal Explanation in Biology: More Than Mechanisms
Dominant views in the philosophical literature claim that explanation in biology is largely, if not entirely, mechanistic. Mechanistic explanations appeal to mechanisms, which involve organized sets of entities and activities that produce some phenomenon of interest (Machamer, Darden, and Craver 2000). One motivation for these accounts is that scientists frequently use the term “mechanism” in referring to the causal factors that figure in their explanations. Biologists, of course, use a variety of causal concepts in their explanations–concepts like pathways, cascades, and triggers–however, standard philosophical views interpret all of these concepts as mechanisms. Philosophers freely admit to using the term mechanism to interpret biological concepts like cascades, mediators, modulators, systems, and substrates, claiming that the “term mechanism could do the same work” (Craver 2007, 3). Analyses of these causal concepts are often used by philosophers to clarify features of mechanistic explanation in biology (Bechtel 2011; Bogen and Machamer 2010).
This mechanistic program raises a number of puzzles. If most or all of the causal concepts in biology are well-interpreted as mechanisms: Why do scientists often distinguish the notion of a mechanism from other causal concepts, like pathways and cascades? Why do they consistently use particular causal concepts in some situations, while not in others? Finally, why do they bother using a variety of causal concepts, when the single notion of mechanism would suffice? In this project, I explore three causal concepts that are commonly cited in biological explanations, particularly in the context of molecular biology. These causal concepts include the notion of a mechanism, pathway, and cascade. I argue that these causal concepts involve important distinctions, which need to be appreciated to understand their role in explanation.
My analysis examines a specific example of each of these causal concepts from molecular biology. These examples include a reaction mechanism, metabolic pathway, and signaling cascade. In this context, the notion of a mechanism refers to a causal structure with part-whole relationships, where significant detail is provided, which typically addresses various “how” questions. The notion of a pathway involves sequential modifications of some material substrate, where the “flow” of substrate through pathway is regulated by various factors. Finally, the notion of a cascade involves the amplification of a small initial signal, into a large final output, where the signal gain is under fine control.
More recently, philosophers have expressed concern with the expansive nature of mechanistic explanation and they have sought to identify its limits, strengths, and defining features. This project suggests one way of achieving these goals, viz. by clarifying how the notion of a mechanism is one of many causal concepts that figure in biological explanations.
Bechtel, W. (2011). Mechanism and Biological Explanation. Philosophy of Science. Bogen, J. and P. Machamer (2010). Mechanistic Information and Causal Continuity. In
Causality in the Sciences. Oxford University Press.
Craver, C. F. (2007). Explaining the Brain.
Machamer, P., L. Darden, and C. F. Craver (2000). Thinking About Mechanisms. Philosophy of Science.
University of Calgary / University of California, Irvine