Thus, no mere external sanction, stood the Faith; threefold: from the past it brought its pompous ritual, it appealed by its subtle dogmatic scheme to the intellects, and by its devotion to the hearts of men. Through the mirage of it, when its substance had waned, Copernicus, Galileo, and Harvey had to steer by the compass of the experimental method. This was their chief adversity, and of other adversities I have to speak. The visitor to the Dominican Church of St Catherine at Pisa will see on its walls St Thomas of Aquino with the Holy Scriptures in his hand; prostrate beneath him is Averroes with his Great Commentary, but beside him Plato bearing the Timæus. It was the fortune of the Faith that, of all the treatises of Plato, the Timæus, the most fantastic and the least scientific, should have been set apart to instruct the medieval world; that the cosmical scheme of the Timæus, apparelled in the Latin of Chalcidius,—for there were then no Greek texts in the libraries of the West,—should for some 500 years have occupied that theoretical activity which Aristotle regarded as the highest good of man[6]. Again, those works of. Aristotle which might have made for natural knowledge fell out of men’s hands[7], while in them, as Abélard tells us of himself, lay the Categories, the Interpretation, and the Introduction of Porphyry to the Categories, all in the Latin of Boetius[8]; treatises which made for peripatetic nominalism, but whereby men were versed rather in logic and rhetoric than in natural science. Thus Plato’s chimera of the human microcosm, a reflection of his theory of the macrocosm, stood beside the Faith as the second great adversary of physiology. The influence of authority, by which Europe was to be welded together, governed all human ideas. As in theology was the authority of the Faith, so in the science and medicine of the first period of the Middle Ages was that of the neo-platonic doctrines, and, in the second period, of the Arabian versions of Galen and of Aristotle; furthermore in this rigid discipline metallic doctrine almost necessarily overbore life and freedom. It is not easy for us to realise a time when intellectual progress—which involves the successive abandonment of provisional syntheses—was unconceived; when truths were regarded as stationary; when reasons were not tested but counted and balanced; when even the later Averroists found final answers either in Aristotle or in Galen[9]. Thus in the irony of things it came to pass that Harvey was withstood by the dogma of Galen who, in his own day, had passionately appealed from dogma to nature.