2. Contributing, without doubt, largely to that indistinctness of ideas, and to the low value put upon physical science, was the mysticism common to the early and the mediæval Church, and to the world at large for many hundred years--the mysticism, that is to say, the habit of assigning supernatural agencies to the various phenomena of Nature, and of regarding them as subject to the vicissitudes of arbitrary will rather than as following out the workings of a consistent orderly plan. There is no need of any attempt to show how fatal such a spirit is to science, nor how that spirit seemed for a long while to dominate the world. "It changed physical science to magic; astronomy to astrology; the study of the composition of bodies to alchemy; and even mathematics was changed till it became the contemplation of the spiritual relations of number and figure." That the Church was not, as has been often charged, responsible for this spiritualizing temper of the age is apparent to any one familiar with the development of Greek philosophy and with the history of the superstitions of the Roman Empire. Nevertheless, it is also true that that temper has been increased in the past and is fostered to-day by the undue emphasis which the Church has placed upon the miraculous character of early Christianity. 3. We notice in the history of the thought of this period, both in the Church and in the world at large, a disposition rather to examine, criticise, and comment upon the work of others, than to do investigating and thinking of one's own. That such a spirit should be found in the Church is not to be wondered at, for the authority of Christ and his apostles would seem to leave no room for originality of thinking on religious subjects, and the sacred Scriptures would give abundant scope for the exercise of the highest learning and of intellectual penetration in interpreting. But the same tendency is noticed outside of the Church, as the great schools of interpreters of Aristotle and of Plato, and the large volumes of abstracts and compilations from preceding writers, bear witness. But when vast learning and ability are expended, rather on such labors than on investigation into the secrets of Nature, science does not thrive. 4. And once again we observe the gradually increasing dogmatic tendency of the Church, the claim to be the repository of all knowledge, the stifling of thought, and of investigation into what might lead men away from the truth and the "faith once delivered to the saints." It seemed best to give in detail these four evident reasons for the barrenness of science during those centuries, because, as I said, the same things to-day, though with decreasing force, interfere with the progress of science and the extension of scientific method. I shall refer to them again a little further on.