The beauty of nature discovered and appreciated, interest began to be evinced in the relationship existing between the various phenomena and there arose a desire to obtain ocular proof of what was written in the venerable books--perhaps even make new discoveries. The first man of any importance in this direction was the German Albrecht Bollstaedt (Albertus Magnus), who, although he contributed more than any other man to the promulgation of Aristotelian philosophy, wrote a book on natural history founded on personal observation; his great English contemporary, however, Roger Bacon, is the true father of modern experimental science. It was he who coined the expression "scientia experimentalis," and framed the principle that all research must be based on the study of nature. He maintained that experience was the "mistress of all sciences," and said: "I respect Aristotle and account him the prince of philosophers, but I do not always share his opinion. Aristotle and the other philosophers have planted the tree of science, but the latter has not by any means put forth all its branches or matured all its fruit." This thought, though it seems to us self-evident, was of great moment in the age of scholasticism. Bacon spent ten years in prison; but in spite of everything, he was so much under the influence of scholasticism that he considered it the task of philosophy to adduce evidence for the truth of the Christian dogma. Here it is essential roughly to sketch the essence of the philosophical thought of that period, and point out the way which led from the Christianity of the Fathers of the Church and scholasticism to the religion of unhistorical Christianity, the so-called mysticism. Scholasticism had reached its climax in the thirteenth century; universities were founded in Paris, Oxford and Padua, and he who aspired to the full dignity of learning had to take his degrees there; even Eckhart did not neglect to obtain his scholastic education in Paris.