All this accumulation of physical and historical knowledge has not failed to react upon our study of the human mind itself. In books of logic the score of centuries between Aristotle and Whately saw less advance than the few years between Whately and Mill. In psychology the work of Fechner and Wundt and Spencer belongs to the age in which we are now living. When to all this variety of achievement we add what has been done in the critical study of literature and art, of classical and Biblical philology, and of metaphysics and theology, illustrating from fresh points of view the history of the human mind, the sum total becomes almost too vast to be comprehended. This century, which some have called an age of iron, has been also an age of ideas, an era of seeking and finding the like of which was never known before. It is an epoch the grandeur of which dwarfs all others that can be named since the beginning of the historic period, if not since Man first became distinctively human. In their mental habits, in their methods of inquiry, and in the data at their command, "the men of the present day who have fully kept pace with the scientific movement are separated from the men whose education ended in 1830 by an immeasurably wider gulf than has ever before divided one progressive generation of men from their predecessors."[2] The intellectual development of the human race has been suddenly, almost abruptly, raised to a higher plane than that upon which it had proceeded from the days of the primitive troglodyte to the days of our great-grandfathers. It is characteristic of this higher plane of development that the progress which until lately was so slow must henceforth be rapid. Men's minds are becoming more flexible, the resistance to innovation is weakening, and our intellectual demands are multiplying while the means of satisfying them are increasing. Vast as are the achievements we have just passed in review, the gaps in our knowledge are immense, and every problem that is solved but opens a dozen new problems that await solution. Under such circumstances there is no likelihood that the last word will soon be said on any subject. In the eyes of the twenty-first century the science of the nineteenth will doubtless seem very fragmentary and crude. But the men of that day, and of all future time, will no doubt point back to the age just passing away as the opening of a new dispensation, the dawning of an era in which the intellectual development of mankind was raised to a higher plane than that upon which it had hitherto proceeded.