Reading this post by Andrew Gelman on “reverse causal questions” helps to sharpen some of my comments here about “causes of effects” research designs. It’s not just that I am transgressing the norms of mainstream comparative politics by arguing that ethnic voting explains the results of GE13, but as Gelman and Imbens write (PDF),

[a question of the type “what explains GE13?”] does not in general have a well-defined answer, even in a setting where all possible data are made available

They note, though, that these sorts of questions are nevertheless integral to the process of scientific discovery.

the search for causal explanations is, in statistical terms, an attempt to improve our models so as to reproduce the patterns that we see in the world

The entire Gelman and Imbens essay is worth a close read.