  Once Descartes had presented his metaphysics, he felt free to proceed with the publication of his entire physics. However, he needed first to teach it to speak Latin (3:523), the lingua franca of the seventeenth century. He hatched a scheme to publish a Latin version of his physics (the Principles) together with a scholastic Aristotelian work on physics, so that the comparative advantages would be manifest. For this purpose, he chose the Summa philosophiae of Eustace of St. Paul. That part of his plan never came to fruition. His intent remained the same: he wished to produce a book that could be adopted in the schools, even Jesuit schools such as  La Flêche (3:233, 523). Ultimately, his physics was taught  in the Netherlands, France, England, and parts of Germany. For the Catholic lands, the teaching of his philosophy was dampened when his works were placed on the Index of Prohibited Books in 1663, although his followers in France, such as Jacques Rohault (1618–72) and Pierre Regis (1632–1707), continued to promote Descartes' natural philosophy.