The principle of simplicity for Qutb al-Din Shirazi

This paper seeks to show how Qutb al-Din Shirazi, a prominent astronomer of the Islamic age of science, employed the principle of simplicity in choosing among rival planetary models. Following some previous studies, we distinguish syntactic and ontological accounts of simplicity. Shirazi explicitly refers to these methodological principles and utilizes them to reduce the number of orbs in the planetary models. We provide cases where Shirazi applies the former account of simplicity, and others where he uses the latter. In some complicated cases, however, he appeals to a third kind of simplicity in favor of conceptual consistency. We argue that retaining the uniform motion of orbs plays a critical role in his favoring a particular account of simplicity.