Galileo's treatise on "The Authority of Scripture in Philosophical Controversies" was written at a time when the Copernican theory of the constitution of the universe was engaging the attention of the world. A Benedictine monk, Benedetto Castelli, called upon to defend the theory at the grand-ducal table of Tuscany, asked Galileo's assistance in reconciling it with orthodoxy. His answer was an exposition of a formal theory as to the relations of physical science to Holy Writ. This answer was further amplified in the "Authority of the Scripture," addressed in 1614 to Christina of Lorraine, Dowager Grand-Duchess of Tuscany, an able and acute defence of his position. A year later another monk laid Galileo's letter to Castelli before the Inquisition, whereupon the philosopher was summoned by Pope Paul V. to the palace of Cardinal Bellarmine, and there warned against henceforth holding, teaching, or defending the condemned doctrine. Nevertheless, in a few years Galileo (see SCIENCE, vol. XV) had to suffer trial and condemnation by the Inquisition for publishing his "Dialogues on the System of the World," which gave the Ptolemaic theory its death-blow. _I.--THE DEFENDERS OF FALLACY_ Some years ago I discovered many astronomical facts till then unknown. Their novelty and their antagonism to some physical propositions commonly received by the schools did stir up against me many who professed the vulgar philosophy, as if, forsooth, I had with my own hand placed these things in the heavens to obscure and disturb nature and science. These opponents, more affectionate to their own opinion than to truth, tried to deny and disprove my discoveries, which they might have discerned with their own eyes; and they published vain discourses, interwoven with irrelevant passages, not rightly understood, of the sacred Scriptures. From this folly they might have been saved had they remembered the advice of St. Augustine, who, dealing with celestial bodies, writes: "We ought to believe nothing unadvisedly in a doubtful point, lest in favour of our error we conceive a prejudice against that which truth hereafter may discover to be nowise contrary to the sacred books." Time has proved every one of my statements, and proving them has also proved that my opponents were of two kinds. Those who had doubted simply because the discoveries were new and strange have been gradually converted, while those whose incredulity was based on personal ill-will to me have shut their eyes to the facts and have endeavoured to asperse my moral character and to ruin me.