The background
Dante called Aristotle ‘the Master of those who know’. Aristotle was so regarded by learned men from the time of Aquinas to that of Galileo. If one wished to know, the way to go about it was to read the texts of Aristotle with care, to study commentaries on Aristotle in order to grasp his meaning in difficult passages, and to explore questions that had been raised and debated arising from Aristotle's books. University education had been patterned on those procedures from its very beginning in the thirteenth century. As Aristotle had lived before the Christian era, he was recognized to have been mistaken on some points, but they were not many and theologians had found and corrected them. Aristotle was commonly referred to as the Philosopher, with a capital P; all matters of knowledge belonged to Philosophy just as all matters of faith belonged to Sacred Theology.
Physical science in general constituted ‘natural philosophy’; that is, knowledge of Nature, which was physis in Greek. Aristotle had covered this in several works, notably in his Physics, On the Heavens, Meteorology, and books about the creation and the coming to an end of things. The principles of physical science were determined in Aristotle's Metaphysics, written after he had composed his books on science, since it would not be proper to have science discuss its own principles, and still less to build it on arbitrary principles determined in advance without careful study of nature.
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