Abstract
Among the factors necessary for the occurrence of some event, which of these are selectively highlighted in its explanation and labeled as causes-and which are explanatorily omitted, or relegated to the status of background conditions? Following J. S. Mill, most have thought that only a pragmatic answer to this question was possible. In this paper I suggest we understand this ‘causal selection problem’ in causal-explanatory terms, and propose that explanatory trade-offs between abstraction and stability can provide a principled solution to it. After sketching that solution, it is applied to a few biological examples.