Reichenbach common cause principle

A classical common-cause explanation seeks past variables which screen off a correlation: conditioned on a sufficiently complete common cause, the correlated events become independent. A Bell local causality model adds local dependence on settings and a single compatible past-variable distribution for all measurement contexts. Providing a different setting-dependent screening variable for each pair of settings does not establish that stronger Bell model. The distinction between a causal mechanism and a purely probabilistic screening construction matters when interpreting this principle.