 His views had been criticized by Gottfried Leibniz, with whom he exchanged letters, later published in a book titled "Negotium otiosum seu σκιαμαχία" (1720).Also, during the first part of the 18th century, Stahl's ideas on the non-physical part of the body were disregarded while his mechanistic ideas on the body were accepted in the works of Boerhaave and Hoffmann.As a physician, Stahl worked with patients and focused on the soul, or "anima", as well as blood circulation and tonic motion.