 One major goal of Lange’s book is thus to show that the formal inferences of Aristotelian logic, the syllogistic, can all be captured within the logic of extension, which might now be called propositional logic. Lange accomplishes this in the next few chapters of the book. He does so by using Euler-Gergonne diagrams, which would now be called Venn diagrams—but Lange died before Venn first published the Venn diagrams in 1880 (in “On the Forms of Logical Proposition”, in the journal Mind). In Symbolic Logic, published the following year, Venn remarks: