Causation Across Levels, Constitution, and Constraint

To explain phenomenon R by showing how mechanism M yields output R each time it is triggered by circumstances C, is to give a causal explanation of R. This paper analyses what mechanistic analysis can contribute to our understanding of causation in general and of downward causation in particular. It is first shown, against Glennan, that the concept of causation cannot be reduced to that of mechanism. Second it is shown, against Craver and Bechtel, that mechanistic explanation allows us to make sense of causal processes that cut across levels, either in bottom-up direction where a change in a part of a system causes a change in the whole, or in downward direction where a change at the level of the system causes a change at the level of its parts. I suggest construing a decision's influence on molecules in muscle cells as a global constraint. Microscopic laws determine the detailed evolution of muscle cells and glucose molecules, but this evolution is constrained by the fact that it must be compatible with the action caused by the decision