I meant to address unfinished business from last time. We moderns see hypothesis as central to the scientific method, not least because we are good Newtonians: our natural philosophy assumes its productive function. But in Copernicus' day none of this held. The quadrivium (arithmetic, geometry, music, astronomy) could make use of hypothesis quite frequently, but the relation of the mathematical arts to philosophy was external rather than integral, while the revival of Aristotelianism in a medieval theological context put particular strain on the relation of natural philosophy to theology, where easier Augustinian assumptions of unity no longer held in the wake of Aquinas' metaphysics, and scholars like Bacon were content with a doctrine of two truths: an astronomical hypothesis might be phenomenologically compatible but is not obligated to satisfy a natural philosophical truth. You might say that hypotheses come easily in astronomy, but the stakes are low, while in natural philosophy hypotheses are regarded with suspicion (the stakes are higher). We must be referring to necessary truths, so what is the point of mere hypothesis? It is only with time, and especially in the work of Galileo (as we shall see) that the practical mathematical disciplines become more fully integrated with natural philosophy: perhaps now a hypothesis can be physically informative.