These background conditions are shown to be inconsistent and, on separate account, logically incoherent. I offer a corrective reformulation which also incorporates a strategy for problems like Hesslow's thrombosis case. I also show that Cartwright's recent argument for modifying the condition to appeal to singular causes fails. I propose a unified solution which also handles extreme causes . Undefined conditional probabilities give rise to three good, but non-equivalent, ways of formulating the theory.
Various formulations appear in the literature.
I give arguments to eliminate all but one candidate. Finally, I argue for a crucial new condition clause, and show how to extend the results beyond a simple probabilistic framework.