section_path: Life/Education/Early education/University of Kraków 1491–1495/Contradictions in the systems of Aristotle and Ptolemy
section_name: Contradictions in the systems of Aristotle and Ptolemy
paragraph_text: Contradictions in the systems of Aristotle and Ptolemy
  
  Copernicus's four years at Kraków played an important role in the development of his critical faculties and initiated his analysis of logical contradictions in the two "official" systems of astronomy—Aristotle's theory of homocentric spheres, and Ptolemy 's mechanism of eccentrics and epicycles —the surmounting and discarding of which would be the first step toward the creation of Copernicus's own doctrine of the structure of the universe.