Between the years 1643 and 1649, Princess Elisabeth of Bohemia (1618-80) and Rene Descartes (1596-1650) exchanged fifty-eight letters-thirty-two from Descartes and twenty-six from Elisabeth. Their correspondence contains the only known extant philosophical writings by Elisabeth, revealing her mastery of metaphysics, analytic geometry, and moral philosophy, as well as her keen interest in natural philosophy. The letters are essential reading for anyone interested in Descartes's philosophy, in particular his account of the human being as a union of mind and body, as well as his ethics...