While in philosophical questions related to mathematics, Proclus and Plato were Kepler’s most important inspirational sources, he did not always see Plato and Aristotle as completely opposed, for the latter—in Kepler’s interpretation—also accepted “a certain existence of the mathematical entities” (KGW 14, let. N° 226, p. 265; see Peters, p. 130). To a great extent Kepler understood his mathematical investigations of HM as a continuation of Euclid’s Elements, especially of the analysis of irrati