Causal Tendency, Necessitivity and Sufficientivity: An Updated Review

The tendency of one event F to cause a later event E was explicated by a simple formula in terms of probability by Good (1961/62), more specifically in terms of ‘weights of evidence’ (logarithms of Bayes factors). The argument was based on the concept of causal circuits. The same explication, and a generalization, are reached here without making use of that concept, and the mathematical level is elementary.