 Due in part to Leibniz’s support, Wolff was soon offered, and accepted, a position in Giessen (though he had also been offered positions at Danzig and Wismar) which he intended to take up after visiting his family in Breslau. However, on his homeward journey the occupation of Saxony by Charles XII of Sweden required Wolff to take a detour through nearby Halle in Prussia, whose recently founded university also happened to be in need of a professor of mathematics. Wolff was offered the position and, again with Leibniz’s assistance, was able to extricate himself from his commitment to Giessen, delivering his inaugural lecture at Halle in early 1707. During the next 15 years he enjoyed a prolific period, publishing and lecturing at first primarily in mathematics and natural science, though he began to lecture in philosophy proper around  1710.[2]  Wolff’s first major philosophical textbook was published in 1713, the Vernünfftige Gedancken von den Kräfften des menschlichen Verstandes und ihrem richtigen Gebrauche in Erkäntnis der Wahrheit (Rational Thoughts on the Powers of the Human Understanding and its Propert Use in the Cognition of Truth) [the German Logic, hereafter GL]. In 1720, Wolff published his German textbook on metaphysics, the Vernünftige Gedanken von Gott, der Welt und der Seele des Menschen, auch allen Dingen überhaupt (Rational Thoughts on God, the World and the Soul of Man, and on All Things in General) [the German Metaphysics, hereafter GM]. These were followed by further German textbooks on ethics (1720), politics (1721), and physics (1723).