The earliest tracts of Aristotle to reach the reviving West were the logical works—the Logica Vetus—rendered into Latin by Boethius during the sixth century. A good deal of Boethius’ work in mathematics and astronomy, as well as his Commentaries on the logic of Aristotle and Porphyry, were available in the earliest middle ages. In the early twelfth century Aristotle’s Posterior Analytics—part of the Logica Nova—were translated into Latin. Then in 1126 Adelard of Bath translated the 15 books of Euclid’s Elements from the Arabic into Latin. In short, logical studies, and the analysis of cogent argumentation, were themselves responsible for much of the intellectual quickening which we now recognize as the medieval revival of learning. The Schoolmen were very early aware of the logical distinctions to be drawn between knowledge of facts and appraisals of valid argument. They knew the difference between factual proofs and logical consistency. And they realized that consistent consequences might be shown to follow from factually untrue premises. They could also detect logical inconsistencies in arguments generated invalidly from factually true premises. These distinctions, pellucidly clear in Aristotle’s own works, reinforced the cleavage between (1) the dogmatic Truths which had been injected into the ‘Christianized’ cosmology of The Philosopher, and (2) the logical and mathematical consistency so obvious in the treatises of Ptolemaic astronomy. It often happened that scientific commentators like Adelard of Bath and Hugh of Victor, as well as Anselm, Richard of St. Victor and Abelard sought to set out their subject matters in accordance with a kind of mathematical-deductive-logical method of exposition. Thus, to anticipate Galileo, Salviati is made to say of the Ptolemaic theory that