FIRST DAY.

Interlocutors,

SALVIATI, SAGREDO, AND SIMPLICIO.

A small horizontal woodcut ornament with scrolling motifs.

SALV. It was the conclusion and the appointment made yesterday that on this day we should discuss, as distinctly and particularly as we are able, the natural reasons and their effectiveness which have been produced thus far by both sides—by the supporters of the Aristotelian Aristotelian: Referring to the ancient Greek philosopher Aristotle, whose views dominated science for centuries. and Ptolemaic Ptolemaic: Referring to Claudius Ptolemy, who proposed the Earth-centered model of the universe. position, and by the followers of the Copernican System. Copernicus considers the Earth to be a globe similar to a planet. And because Copernicus, by placing the Earth among the moving bodies of the Heavens, makes it also a globe similar to a planet, it will be well for the beginning of our considerations to be the examination of the force and energy in the Peripatetic Peripatetic: A name for the followers of Aristotle, derived from his habit of walking about while teaching. arguments when they demonstrate how such an assumption is entirely impossible. Celestial substances are unchangeable, and elementary ones are changeable, as is necessary in nature according to the mind of Aristotle. This is because they find it necessary to introduce into nature substances that are different from one another: namely, the Celestial and the Elementary. The former is impassive original: "impassibile"—meaning it cannot be changed or affected by external forces and immortal, while the latter is changeable and decaying. He treats this argument in his books On the Heavens Aristotle's treatise De Caelo, introducing it first through discourses depending on certain general assumptions, and later confirming it with experiences and demonstrations.