  The point of departure for Autrecourt’s physics is a thesis which strikes him as more probable than its opposite, namely that all things are eternal. Autrecourt assures the reader that he is speaking as a natural philosopher, and that he is not contradicting Catholic faith. One of the implications of his thesis is that there is no generation or corruption in the universe. Autrecourt refutes Averroes’s (and Aristotle’s) doctrine of prime matter in which substantial forms are generated and corrupted. He replaces the theory of hylemorphism, which attributes the coming-to-be and passing-away of properties and of objects to forms that begin and cease to exist in matter, by atomism. Change in the natural world is caused by the movement of atoms. These atoms are to be understood as infinitely small parcels of matter which have properties.