 C. I. Lewis’s definition of coherence, or “congruence” to use his term, can be seen as a refinement and improvement of Ewing’s basic idea. As Lewis defines the term, a set of “supposed facts asserted” is coherent (congruent) just in case every element in the set is supported by all the other elements taken together, whereby “support” is understood not in logical terms but in a probabilistic sense. In other words, \(P\) supports \(Q\) if and only if the probability of \(Q\) is raised on the assumption that \(P\) is true. As is readily appreciated, Lewis’s definition is less restrictive than Ewing’s: more sets will turn out to be coherent on the former than on the latter. (There are some uninteresting limiting cases for which this is not true. For instance, a set of tautologies will be coherent in Ewing’s but not in Lewis’s sense. There cases are not interesting because they are not significant parts of anyone’s actual body of beliefs.)