 In the wake of all these pioneers , Bernoulli produced much of the results contained in Ars Conjectandi between 1684 and 1689 , which he recorded in his diary Meditationes . When he began the work in 1684 at the age of 30 , while intrigued by combinatorial and probabilistic problems , Bernoulli had not yet read Pascal 's work on the " arithmetic triangle " nor de Witt 's work on the applications of probability theory : he had earlier requested a copy of the latter from his acquaintance Gottfried Leibniz , but Leibniz failed to provide it . The latter , however , did manage to provide Pascal 's and <unk> 's work , and thus it is largely upon these foundations that Ars Conjectandi is constructed . Apart from these works , Bernoulli certainly possessed or at least knew the contents from secondary sources of the La <unk> ou l ’ Art de <unk> as well as Graunt 's Bills of Mortality , as he makes explicit reference to these two works . 
