Ways of knowing

"The physicist proves the earth to be round by one means [(medium)], the astronomer by another: for the latter proves this by means [(media)] of mathematics, e.g., by the shapes of eclipses, or something of the sort; while the former proves it by means [(medium)] of physics, e.g., by the movement of heavy bodies towards the center [(medium!)], and so forth. Now the whole force of a demonstration, which is a syllogism producing science, as stated in Poster. i, text. 5, depends on the mean [(medio)]. And consequently various means [(media)] are as so many active principles, in respect of which the habits of science are distinguished."

     St. Thomas Aquinas, Summa theologiae I-II.54.2.ad 2, FEDP as modified by (?) the Aquinas Institute translator.