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...