∗Forthcoming in a Minds and Machines special issue on “Causality, Uncertainty and Ignorance”. Thanks to audiences at Konstanz and Sydney, to the Russellian Society Discussion Group, and

Is the common cause principle merely one of a set of useful heuristics for dis-covering causal relations, or is it rather a piece of heavy duty metaphysics, capable of grounding the direction of causation itself? Since the princi-ple was introduced in Reichenbach’s groundbreaking work The Direction of Time (1956), there have been a series of attempts to pursue the latter program—to take the probabilistic relationships constitutive of the princi-ple of the common cause and use them to ground the direction of causation. These attempts have not all explicitly appealed to the principle as originally formulated; it has also appeared in the guise of independence conditions, counterfactual overdetermination, and, in the causal modelling literature, as the causal markov condition. In this paper, I identify a set of difficulties for grounding the asymmetry of causation on the principle and its descen-dents. The first difficulty, concerning what I call the vertical placement of causation, consists of a tension between considerations that drive toward