 Avicenna synthesized the various strands of philosophical thought he inherited—the surviving Hellenic traditions along with the developments in philosophy and theology within Islam—into a self-consistent scientific system that explained all reality. His scientific edifice rested on Aristotelian physics and metaphysics capped with Neoplatonic emanationism in the context of Ptolemaic cosmology, all revised, re-thought, and critically re-assessed by him. His achievement consisted in his harmonization of the disparate parts into a rational whole, and particularly in bringing the sublunar and supralunar worlds into an intelligible relation for which he argued logically. The system was therefore both a research program and a worldview.