Historical and Methodological Details on the De Motu Gravium Naturaliter Descendentium in Torricelli’s Opera Gometrica (1644)

In this paper, we deal with Torricelli’s principle in mechanics according to which two heavy bodies linked together cannot move by themselves unless their common centre of gravity descends. At the beginning of the De motu gravium naturaliter descendentium, in his Opera geometrica (1644), Evangelista Torricelli (1608–1647) expressed this principle in a very brief section entitled Praemittamus. Our aim is to sustain the idea that Torricelli was constructing a general view of a kind of physics based on general principles, of which the previous one is the most important and explicit statement. In our discussion, the following themes are addressed: (1) a comparison between the Torricelli’s principle and the virtual work principle; (2) the role of Torricelli principle within the history of the virtual work principle; (3) the logic behind the demonstrations offered in physics relying on general principles such as that of Torricelli.