 The most famous letter written to Beeckman in 1619 dates from 26 March of that year. In this letter Descartes announces his plan to expound an “entirely new science [scientia penitus nova], by which all problems that can be posed, concerning any kind of quantity, continuous or discrete, can be generally solved” (AT X, 156). As he elaborates on how this new science will proceed, Descartes clarifies that his solutions to the problems of discrete and continuous quantities—that is, of arithmetic and geometry, respectively—will vary depending on the nature of the problem at hand. As he puts it,