1 The Hellenistic and Alexandrian Influences on Johannes’ Kepler Work Panagiotis Papaspirou * , Xenophon Moussas † * PhD Candidate, Section of Astrophysics, Astronomy and Mechanics, Faculty of Physics, National and Capodistrian University of Athens, Panepistimiopolis, GR 15783 Zographos, Athens, Greece. E-mail: p.papaspirou973@gmail.com † Professor in Space Physics, Director of the Astronomical Observatory of the University of Athens, Director of Astrophysics Laboratory, Section of Astrophysics, Astronomy and Mechanics, Faculty of Physics, National and Capodistrian University of Athens, Panepistimiopolis, GR 15783 Zographos, Athens, Greece. E-mail: xmoussas@phys.uoa,gr Abstract We investigate the close relationships between the astronomical and scientific work of the famous great astronomer Johannes Kepler and the major scientific in general, and astronomical in particular, achievements that took place within the Hellenistic period and the Alexandrian epoch that followed immediately, that is from the Battle of Actium until the death of the scholar and polymath Hypatia. We propose that the Hellenistic Philosophy and Science, as being developed by Giants of Mind, such as Hipparhus of Rhodes, Archimedes of Syracuse, Aristarchus of Samos, Apollonius of Perga, Menelaus of Alexandria, Euclid of Alexandria, Ptolemy of Alexandria, and by philosophers such as Plotinus and Proclus, as well as all the other Neoplatonic philosophers of this era, instills and permeates Kepler’s philosophical view of Cosmos, and at the same time sets the guidelines and paves the way of his lifelong scientific endeavor upon discovering and determining the true laws of planetary motion within a Heliocentric Universe. Johannes’ Kepler work is deeply rooted within these epochs, his philosophical views, his religious beliefs, his physical and astronomical insights about the Universe, all of them can be traced already in the Hellenistic and Alexandrian science. Although the time interval between his era and the great achievements of the Hellenistic and Alexandrian scientists, mathematicians and philosophers spans many centuries, measured according to the flow of historical time, in reality the spirit of these eras irrigated continuously all of the great civilizations which inherited the Hellenistic tradition, that is the Byzantine, the Arabic and Islamic, and the European civilization, giving birth to the Renaissance of the 12 th century and to the Renaissance of the 14 th century. Kepler, by following his own scientific routes of inquiring, has to be confronted with this tradition, either by accepting some parts of it, or by rejecting specific dogmas and conceptions about the nature and the structure of Cosmos entailed in this tradition, in order to proceed to the theoretical astronomic endeavor of a logically comprehensible, and beautifully ordered Universe, which is subject to unifying physical principles of symmetry, harmony, proportion and analogy, as well as physical laws. Kepler makes the decisive step towards