This is the first book length defence of a counterfactual theory of causation. The analysis defended is new. It expresses the idea that, independent of its competitors, a cause raises the chance of an effect over its mean background chance by a complete causal chain. The analysis depends upon a novel development of David Lewis's Theory of Counterfactuals. One consequence of the analysis is that causation is not transitive. Causation is also nonsymmetric. The counterfactual basis of causal nonsymmetry is the result of a number of different, and sometimes interacting, nonsymmetries. The...