Mechanisms 2

Entities and activities compose biological mechanisms. However, the new mechanistic philosophers of science have paid too little attention to activities. Critics have charged that accounts of activities in the new mechanism literature are philosophically uninformative and opaque. This paper defends a novel account of causally productive activities, which I call the Hybrid Account, that marries the two dominant philosophical approaches to causation: production and difference-making. The Hybrid Account of Activities (HAA) identifies causally productive activities as productive difference-makers to the next stage of a mechanism, and it individuates activities by the types of change they produce.

Recent work by some New Mechanists has proposed that scientists confirm hypotheses about what composes what by pairing the results of "top-down" and "bottom-up" "interlevel interventions. One limitation of this approach is that, at times, scientists are unable to perform both the top-level intervention and the bottom-level detection. What do they do in such situations? We propose that scientist rely on abduction. They postulate entities that they believe will explain "top-level" phenomena. We illustrate this with a case study: Hodgkin and Huxley's determination of the compositional bases of action potentials.

Mechanisms offer a new way of thinking about reductionism. According to the constitutive account, ‘system-level’ phenomena consist of concerted behaviours of mechanistic components. According to the causal mediation account, descriptions as diverse as ‘black box’ phenomena, mechanistic sketches and detailed mechanistic explanations refer to the same causal structure. Under these accounts, terms belonging to different disciplines or explanations may be shown to correspond to one another, thus opening new possibilities for implementing reduction. I provide several examples illustrating how reductionism may proceed and show that even biopsychosocial models, which may seem fundamentally antireductionistic, can sustain reductionism.