ABSTRACT
This chapter explains the natural laws into astronomy are closely linked with the Copernican revolution and the need to provide a criterion for the differentiation between empirically equivalent astronomical theories. Copernicus' notion of law comes from the early medieval reception of Latin writers on astronomy. Ptolemy's models needed to be modified to accommodate changes in the astronomical configurations more than a thousand years after they were constructed. These modifications were cautiously introduced by Islamic astronomers and then slowly transmitted to Europe. Medieval Latin qualitative astronomy and classical Greek mathematical astronomy coexisted independently from each other in the world of scholarly learning throughout the fifteenth and sixteenth centuries. In the history of astronomy the development of theory is typically described as a linear succession from Ptolemaic astronomy, with intermediaries in Arabic astronomy up to Copernicus' heliocentric revolution and Johannes Kepler's final abolition of epicyclic models.
