Among mathematical fields, probability stands out because of its short history and peculiar origins. Startingwith the analysis of games of chance, probability developed as the mathematical theory of uncertainty, andnowadays probabilistic methods impregnate models of random phenomena. Going through the scienti c careerof the Japanese mathematician Kyoshi Itô (1915-2008), we analyze his theory of stochastic analysis from theperspective of a symbiotic relationship between purely curiosity driven and applied research interests.