 To the two kinds of causality described by Salmon there correspond two different levels of explanation: (1) the S-R model, which concerns connections between kinds of events, and (2) causal mechanical explanation, which bears upon single events. It should not pass unnoticed that while explanation of the first level, based on statistical correlations, provides a good basis for prediction, explanation in terms of aleatory causality traces back the history of events after their occurrence. In the Eighties, Salmon thought that only aleatory causality could offer an adequate understanding of causality and regarded the causal mechanical level as genuine explanation, assigning an ancillary role to the S-R level.