 One question arising from a historical point of view is that of exegetical correctness. Can Aristotle’s and Boethius’ theses indeed be traced back to Aristotle and Boethius? Lenzen (forthcoming) believes that Aristotle and Boethius intended the theses named after them as “applicable only to ‘normal’ conditionals with antecedents which are not self-contradictory.” He states correspondingly restricted versions of Aristotle’s theses in the language of modal propositional logic, principles which according to Lenzen (2019) can be found in Leibniz’s writings (after a transformation from Leibniz’s term logic into a system of propositional logic) and where, notation adjusted, ↠ stands for strict implication: