 A key observation for this classificatory enterprise comes from Omori and Sano 2015, where a mechanical procedure is described for turning truth tables using the four generalized truth values of first-degree entailment logic, FDE, see the entries on  truth values  and   relevance logic  and Omori and Wansing 2017, into pairs of positive and negative conditions in terms of containing or not containing the classical truth values 0 and 1. Then, in McCall’s system CC1 a connexive conditional A → B receives a designated value (is true) in a model just in case (i) A does not receive a designated value or B does and (ii) 0 belongs to the value of A iff it belongs to the value of B. In this sense, the connexive implication of Angell-McCall is obtained by adding a condition to the truth condition for Boolean implication.