 A rather important if under-appreciated early influence on Wolff’s thinking, particularly concerning scientific method, was Ehrenfried Walther von Tschirnhaus (1651–1708). Tschirnhaus, a Saxon nobleman, studied at the University of Leiden where the Cartesian Geulincx was  active,[3]  and was an important member of Spinoza’s circle of friends (among whom he circulated the Ethics). Yet, Tschirnhaus was also an active scientist, mathematician, and inventor, who among other things played a (perhaps the) key role in the discovery of the secret for making porcelain. Tschirnhaus’ principal philosophical work is his Medicina mentis (1687, 2nd ed. 1695), and he characterizes his aim there as outlining a “certain and constant method” for the discovery of all unknown truths. Wolff first gained an interest in reading the Medicina mentis while at Gymnasium, but it was only after taking up his mathematical studies in Jena in 1699 that he found himself able to profit from reading it. Wolff evidently read the text with great interest and care, marking his own copy with comments and queries and later preparing an excerpted text for use in lectures for students without the requisite mathematical background. Wolff even sought out Tschirnhaus himself during an Easter book fair in Leipzig to press him with his concerns relating to his method. (After Tschirnhaus’ death in 1708 Wolff inquired as to the status of his manuscripts but was disappointed to learn that, like Spinoza, he had ordered them destroyed).