The ideas of Nicholas of Cusa with regard to knowledge and the liberty of judgment in things not matters of faith can be very well appreciated from some of his expressions. "To know and to think," he says in one passage, "to see the truth with the eye of the mind is always a joy. The older a man grows, the greater is the pleasure it affords him; and the more he devotes himself to the search after truth, the stronger grows his desire of possessing it. As love is the life of the heart, so is the endeavor after knowledge and truth the life of the mind. In the midst of the movements of time, of the daily work of life, of its perplexities and contradictions, we should lift our gaze fearlessly to the clear vault of heaven and seek ever to obtain a firmer grasp of, and keener insight into, the origin of all goodness and duty, the capacities of our own hearts and minds, {22} the intellectual fruits of mankind throughout the centuries, and the wondrous works of nature around us; but ever remembering that in humility alone lies true greatness, and that knowledge and wisdom are alone profitable in so far as our lives are governed by them." [Footnote 1] It is no wonder, then, that the time was ripe for Copernicus and his great work in astronomy, nor that that work should be accomplished while he was a canon of a cathedral and for a time the vicar-general of a diocese. It is now nearly five years since Father Adolph Muller, S.J., professor of Astronomy in the Pontifical Gregorian University of Rome, and director of a private observatory on the Janiculum in that city, wrote his historical scientific study [Footnote 2] of the great founder of modern astronomy. The book has been reviewed, criticized and discussed very thoroughly since then, and has been translated into several languages. The latest translation was into Italian, the work of Father Pietro Mezzetti, S.J., [Footnote 3] and was published in Rome at the end of 1902--having had the benefit {23} of the author's revision. The historical details, then, of Copernicus's life may be considered to have been cast into definite shape, and his career may be appreciated with confidence as to the absolute accuracy and essential significance of all its features. [Footnote 1: _History of the German People at the Close of the Middle Ages_. By Johannes Janssen Translated from the German by M A Mitchell and A M Christie. Vol I, p. 3.] [Footnote 2: _Nikolaus Kopernicus, Der Altmeister der neueren Astronomie, Ein Lebens und Kultur Bild_. Von Adolf Muller, S.J.] [Footnote 3: Professor of Astronomy and Physics at the Pontifical Leonine College of Anagni]