From the mid-1600s to the beginning of the eighteenth century, there were two main circles of German scholars which focused extensively on diagrammatic reasoning and representation in logic. The first circle was formed around Erhard Weigel in Jena and consists primarily of Johann Christoph Sturm and Gottfried Wilhelm Leibniz; the second circle developed around Christian Weise in Zittau, with the support of his students, particularly Samuel Grosser and Johann Christian Lange. Each of these scholars developed an original form of using (...) geometric diagrams in logic. In this paper, I will trace the historical notes of John Venn and other modern logicians back to the original works published in the Weigel and Weise circles and describe the development of using geometric figures for logical reasoning and representation in that period of time. (shrink)

The aspects of Erhard Weigel's Analysis Aristotelica ex Euclide restituta that foreshadowed and helped form some characteristics of symbolic logic are highlighted: first, the idea of a pure form of a logical syllogism or of a mathematical proof and, second, a tentative arithmetisation of some aspects of logic. Also, Weigel's emphasis on the role of symbols and figures in the process of mathematical proof is discussed.