  There are different answers to these questions. Wolfgang Lenzen, e.g., wrote that Leibniz was the most significant logician between Aristotle and Frege, but despite the enormous significance of his logic, he played hardly any role in the history of logic (Lenzen 2004a, 15; cf. also Lenzen 2004b). According to Lenzen, Leibniz’s mature logical theory was present in his Generales Inquisitiones de Analysi Notionum et Veritatum, which was only published in Couturat’s edition of Leibniz’s minor writings and fragments (Leibniz 1903, 356–399). Couturat had already referred to it in his book on Leibniz’s logic which had appeared two years earlier (Couturat 1901). We find similar evaluations by William and Martha Kneale, who in The Development of Logic rank Leibniz among “the greatest of all logicians,” but stress “that his work on logic had little influence for nearly 200 years after he wrote it” (Kneale/Kneale 1962, 320). In the Kneales’ opinion, Leibniz had rather become notorious for claiming to have made great discoveries in logic while there was little published evidence for this claim.