Mental Causation and Intelligibility

I look at some central positions in the mental causation debate - reductionism, emergentism, and nonreductive physicalism - on the hypothesis that mental causation is intelligible. On this hypothesis, mental causes and their effects are internally related so that they intelligibly "fit", analogous to the way puzzle pieces interlock, or shades of red fall into order within a color sphere. The assumption of intelligibility has what I take to be a welcome consequence: deciding among rivals in the mental causation debate could end up to be largely an empirical matter.