The necessity for an intellectual expansion beyond the limits of the Bible was felt very strongly at the time of the Renaissance, and found ample satisfaction in the study of the Greek and Latin classics. There are many reasons why women appear to be more religious than men; and one of them is because women study only one collection of ancient writings, whilst men have been accustomed to study three; consequently that which women study (if such a word is applicable to devotional, uncritical reading) occupies their minds far more exclusively than it occupies the mind of a classical scholar. But, though the intellectual energies of men were for a time satisfied with classical literature, they came at length to look outside of that as their fathers had looked outside of the Bible. Classical literature was itself a kind of religion, having its own sacred books; and it had also its heretics,--the students of nature,--who found nature more interesting than the opinions of the Greeks and Romans. Then came the second great expansion of the human mind, in the midst of which we ourselves are living. The Renaissance opened for it a world of mental activity which had the inappreciable intellectual advantage of lying well outside of the popular beliefs and ideas, so that cultivated men found in it an escape from the pressure of the uneducated; but the new scientific expansion offers us a region governed by laws of a kind peculiar to itself, which protect those who conform to them against every assailant. It is a region in which authority is unknown, for, however illustrious any great man may appear in it, every statement that he makes is subject to verification. Here the knowledge of ancient writers is continually superseded by the better and more accurate knowledge of their successors; so that whereas in religion and learning the most ancient writings are the most esteemed, in science it is often the most recent, and even these have no authority which may not be called in question freely by any student. The new scientific culture is thus encouraging a habit of mind different from old habits, and which in our time has caused such a degree of separation that the most important and the most interesting of all topics are those upon which we scarcely dare to venture for fear of being misunderstood.