Mechanism and Mechanical Explanation in Cell Biology

Robert C. Richardson and Achim Stephan

Recent philosophical discussions often tend to emphasize mechanistic explanation as opposed to reductive explanation. The latter claims to render higher level explanations either redundant or eliminable, depending on whether the higher level explanations are retained as at least approximate (as is the case when we compare Newtonian and Relativistic mechanics) or the higher level explanations are falsified and replaced (as is the case with Aristotelian and Galilean physics, or Newtonian and Relativistic Mechanics). The appeal to mechanistic explanation has a deep history, dating at least to the 17^th century. Sometimes, mechanistic explanation means little more than causal explanation, or explanation in terms of the laws of mechanics. Among Positivists, at the beginning of the 20^th century, the thought was that formalist or structuralist accounts of explanation would capture reductionist models; these were, explicitly, an attempt to capture the idea of mechanistic explanation in a formal mode. The recent reinvigoration of mechanism derives from philosophers who think that the Positivistic approaches to reduction and explanation fail to capture scientific practice (e.g., William Wimsatt, William Bechtel, Robert C. Richardson). Some more recent mechanists (especially Peter Machamer, Lindley Darden, and Carl Craver) assume that mechanistic explanation has a particular structure (this is the MDC model, an acronym for the three authors). We assume we have, say, an organism with a characteristic behavior we want to explain. These behaviors can differ depending on the entities, characteristic activities, and the organization of the containing system. Spatial and temporal organization are also crucial. The result is a schema for understanding mechanistic explanations. Craver says, at one point, "In such schemata, higher level activities (Ψ) of mechanisms as a whole (S) are realized by the organized activities ( Φ) of lower level components (Xs), and these are, in turn, realized by the activities (σ) of still lower level components (Ps)"

We intend to explore the adequacy of these models of mechanistic explanation, in light of the undeniably mechanistic accounts of the behavior of unicellular organisms. First, we ask whether the current model of mechanistic explanation is adequate for the broader range of scientific cases it is intended to cover. This issue has already been raised in an evolutionary context (Skipper, Millstein); we want to assess the question within the context of molecular cell physiology. The specific model offered by Machamer, Darden and Craver (MDC) is designed for neuroscience, and for the issues of reductionism that prevail in philosophy of neuroscience. One concern is how generally the MDC model applies. Second, and more fundamentally, we ask whether mechanistic explanation actually fits a reductive mode of explanation. We have argued (with Fred Boogerd, Frank Bruggeman, and Hans Westerhof) in a pair of forthcoming articles that there are emergent phenomena in cell biology that are also mechanistically determined. The key thought is that cell biology exhibits mechanistic explanations of emergent phenomena. We have shown there is one scientifically and philosophically interesting sense in which this is so. We propose to further explore the thought (hypothesis) that cell biology exhibits emergent phenomena that are mechanistically explicable. If this is so, then the context in which models of mechanistic explanation have been developed may not exhibit the richness they deserve. The goal would be to develop a more enhanced understanding of both mechanism and emergentism, one which moves beyond the more standard mechanism/reductionism and mechanism/eliminativism dichotomies.