Editing Simplicius of Cilicia (section)

=== Astronomy ===
Aristotle had already taken the view that mathematics, as a superordinate science, was allowed to provide axioms to a subordinate science such as astronomy and was responsible for the justification and explanation of astronomical phenomena; the superordinate science knows the causes, the subordinate only the facts. Following this principle, Aristotle used geometric definitions and insights for his cosmological explanations. Philoponus turned against his method of argumentation, believing that a mathematical argument related to physics could be invalidated by pointing to the nature of physical reality, which so limited the mathematical possibility that the argument lost its basis. Thus, mathematical principles are not fully applicable in the physical world. This view met with vehement criticism from Simplicius, who called for an unimpeded transition from physics to its mathematical principles and, conversely, an unrestricted application of mathematical principles to physics, and especially to astronomy. He considered [[deductive reasoning]] to be more important than gaining insights through [[induction (philosophy)|induction]]. Accordingly, he presented Aristotelian cosmology as a strictly deductive system.<ref>Frans A. J. de Haas: ''Mathematik und Phänomene. Eine Polemik über naturwissenschaftliche Methode bei Simplikios''. In: ''Antike Naturwissenschaft und ihre Rezeption'' 10, 2000, S.&nbsp;107–129.</ref>

In astronomy, Simplicius, like Aristotle, presupposed the [[geocentrism]] that was prevalent in antiquity that the Earth was at rest in the center of the universe. With regard to the movements of the stars, however, he deviated from the Aristotelian model, which envisages transparent, uniformly rotating hollow balls (spheres) arranged concentrically around the center of the world, to which the stars are attached, keeping the celestial bodies in their constant orbits. Simplicius thought that this concept was partly superseded by the later astronomical findings presented by [[Claudius Ptolemy|Ptolemy]]. But he did not consider Ptolemy's model to be the final solution either. He was of the opinion that none of the previous theories offered a satisfactory account and explanation of the planetary motions, none was necessarily and demonstrably correct. His own theory also failed to meet his criteria for scientific proof. In contrast to Aristotle, he assumed an axial rotation of all celestial bodies and did not consider their circular movements to be [[concentric spheres|homocentric]]. According to his idea, only the sphere of the fixed stars revolves around the center of the universe; the planets, which in ancient times also included the Sun and the Moon, perform a more complex motion that involves at least one circular motion that is not centered on the Earth.{{sfn|Bowen|2012|pp=14, 27–38}}

Following on from Aristotle, Simplicius distinguished between the approaches of two types of natural scientists: the "physicist" ''(physicós),'' by which he meant a [[natural philosophy|natural philosopher]], and the "mathematician", i.e. a non-philosopher, who tries to grasp physical conditions with mathematical means. A special case of such a “mathematician” is the astronomer. Both types of researchers study the same subject, but in different ways. The "physicist" inquires into the nature of the [[celestial spheres]] and heavenly bodies, he considers them from a qualitative point of view, while the astronomer deals with quantitative points of view, relying on arithmetic and geometrical reasoning. The "physicist" asks about causal connections, the astronomer limits himself to a description that is intended to do justice to the observed phenomena without explaining them causally. Simplicius considered the natural-philosophical, "physical" approach to be the only scientifically profitable one. He believed that astronomers should not be satisfied with devising "hypotheses" – mere rules of calculation – but should use a physical theory well founded by causal argumentation as the starting point for their considerations. Only such a well-founded astronomy can provide real insights. It must be able to explain all observed phenomena, including apparent variations in the size of celestial bodies.{{sfn|Bowen|2012|pp=38-52}}