 The well-known principle of total evidence now dictates that all relevant evidence should be taken into consideration when computing probabilities. Since it cannot be excluded at the outset that the evidence represented by \(E_1\)–\(E_3\) may be relevant to the probability of the information sets \(S\) and \(S'\), the probability of the smaller set is not \(P(A_1,A_2)\) but rather \(P(A_1,A_2 \mid E_1,E_2)\). Similarly, the probability of the larger set is not \(P(A_1,A_2,A_3)\) but rather \(P(A_1,A_2,A_3  \mid E_1, E_2, E_3)\).