We will now examine this interesting letter more closely. When we call to mind the disquisitions on the relation of Scripture to science, which Galileo wrote to Castelli in 1613, and to the Grand Duchess Christine in 1615, the very beginning is a misrepresentation only excusable on the ground of urgent necessity. He says: “The incorrectness of the Copernican system should not in any case be doubted, especially by us Catholics, for the inviolable authority of Holy Scripture is opposed to it, as interpreted by the greatest teachers of theology, whose unanimous declaration makes the stability of the earth in the centre, and the revolution of the sun round it, a certainty. The grounds on which Copernicus and his followers have maintained the contrary fall to pieces before the fundamental argument of the Divine omnipotence. For since this is able to effect by many, aye, endless means, what, so far as we can see, only appears practicable by one method, we must not limit the hand of God and persist obstinately in anything in which we may have been mistaken.[587] And as I hold the Copernican observations and conclusions to be insufficient, those of Ptolemy, Aristotle, and their followers appear to me _far more delusive and mistaken, because their falsity can clearly be proved without going beyond the limits of human knowledge_.”[588] After this introduction Galileo proceeds to answer Rinuccini’s question. He treats that argument against the Copernican system as delusive, and says that it originates in the assumption that the earth stands still in the centre, and by no means from precise astronomical observation. _He refutes, therefore, the scientific objection to the new doctrine._ Speaking of the assumed discovery of Pieroni, he says, that if it should be confirmed, however small the parallax may be, _human science must draw the conclusion from it that the earth cannot be stationary in the centre_. But in order to weaken this dangerous sentence, he hastens to add, that if Pieroni might be mistaken in thinking that he had discovered such a parallax of a few seconds, those might be still more mistaken who think they can observe that the visible hemisphere never varies, not even one or two seconds; for such an exact and certain observation is utterly impossible, partly from the insufficiency of the astronomical instruments, and partly from the refraction of the rays of light.