Letters of Euler to a German Princess

At the start of their correspondence, Euler's royal pupil - the German princess - had little or no knowledge of natural philosophy and mathematics. The letters in this text show how Euler takes his pupil back to the basic notions of distance, time and velocity. Euler then progresses onto the more difficult topics of physics: light and colour; sound; gravity; electricity; and magnetism. From physics, he leads on to natural philosophy: the nature of matter; the origin of forces; and the rival worldviews of Newtonians and Cartesians. Here Euler seeks to separate the mathematical achievement of Newton, about which he had doubts and reservations, from the physical interpretation put on his work by others. The letters go beyond natural philosophy into metaphysics, dealing with the mind-body problem, free will and determinism, the nature of spirits, and the operation of providence in the world of nature. Here, Euler thinks, unaided human reason does not take us very far - some questions may be left unanswered awaiting divine illumination. In particular, he is very suspicious of the metaphysical system of Leibniz and Wolff.