 In 1609, Galileo began his work with the telescope. There are many ways to describe Galileo’s findings, and many interpreters have taken this to be an interlude irrelevant to his physics. However, they are remarkable insofar as they are his start at dismantling the celestial-terrestrial distinction entrenched in Aristotelian cosmology (Feyerabend 1975). Perhaps the most unequivocal case of this is when he analogizes the mountains on the moon to mountains in Bohemia in the Starry Messenger. Also crucial was his discovery of the four moons circling Jupiter, which lent credence to the Copernican system since it meant that a planet-moon arrangement was not unique to the Earth. The abandonment of the dichotomy between heavens and earth implied that all matter, whether celestial or terrestrial, is of the same kind. Further, if there is only one kind of matter, there can be only one kind of natural motion—one kind of motion that this matter has by nature. So it has to be that one law of motion will hold throughout the terrestrial and celestial realms. This is a far stronger claim than he had made in 1590, which concerned only the terrestrial elements.