"No other poet has ever combined the loftiest poetry with the discussion of such complicated topics in all branches of learning. In one place we find a long discussion of the origin and development of life, which, naive and scholastic as it is, shows some lines of resemblance to the modern doctrines in biology; in another place there is a learned discussion between the poet and Beatrice concerning the cause of the spots in the moon, in which an actual experiment in optics is given." The first passage to which Professor Kuhns refers, while containing many speculative elements, is a discussion of certain important basic problems in biology that have always appealed to thinking men at every period of the history of science, and never more so than in our own day. They must still be considered undecided, though many volumes have been written on them in the last century. There are thoughts in Dante's exposition of the subject that are startling enough to the modern biologist, and that make it clear how much men's minds run along the same grooves in facing questions that we are prone to think have occurred to men only in the last {349} few generations. The other quotation to which Professor Kuhns refers deserves to be quoted entire. It is perhaps even more striking because of its actual description of an experiment in optics, which shows how much this great poetic intelligence of the medieval time, usually supposed to be so abstracted and occupied with things other-worldly and supernal, living his intellectual life quite beyond the domain of sense, still remembered the teachings of his university days, and even recalled the details of demonstrations that he had seen. The passage occurs in the II. canto of the Paradiso, beginning with line 97: "Take thou three mirrors, two of them remove From thee an equal distance, and the last Between the two, and further from thee move; And turned towards them let a light be cast, Behind thy back, upon those mirrors three, So that from all reflected rays are passed. Then, though the light which furthest stands from thee May not with them in magnitude compete, Yet will it shine in brightness equally." It is easy to understand, then, that Professor Kuhns should have been enthusiastic with regard to Dante's knowledge of science. He says: "The whole structure of Hell, Purgatory, and Paradise shows a thorough knowledge of the Ptolemaic system; and we invariably find astronomical facts, mingled with classical quotations, in the description of stellar phenomena. But not only in specific passages do we find evidence of Dante's love for science, but in brief allusions to the various aspects of nature--metaphors, {350} figures, descriptions--a word or two is added, giving the cause of the phenomenon in question. Examples of this abound."