and when pioneering adventure and general travel in a world of open avenues were already beginning to have that liberating effect which has increased with every passing century.

Closely allied with the two elements already noted is a third: the increase of knowledge, which, as in the case of astronomy, threw discredit upon the superior claims of antiquity and made modern men seem wiser than their sires. For ages the conviction had held the ground that the ancients were the wisest men who ever lived and that we, their children, were but infants in comparison. When, therefore, the Copernican astronomy proved true, when the first terrific shock of it had passed through resultant anger into wonder and from wonder into stupefied acceptance, and from that at last into amazed exultation at the vast, new universe unveiled, the credit of antiquity received a stunning blow. So far was Aristotle from being "the master of those who know" whom the medievalists had revered, that he had not even known the shape and motion of the earth or its relation with the sun. For the first time in history the idea emerged that humanity accumulates knowledge, that the ancients were the infants, that the moderns represent the age and wisdom of the race. Consider the significance of those words of Pascal in the seventeenth century: "Those whom we call ancient were really new in all things, and properly constituted the infancy of mankind; and as we have joined to their knowledge the experience of the centuries which have followed them, it is in ourselves that we should find this antiquity that we revere in others." [10] For the first time in history men turned their faces, in their search for knowledge, not backward but forward, and began to experience that attitude which with us is habitual—standing on tip-toe in eager expectancy, sure that tomorrow some new and unheard of truth will be revealed.

New inventions, new discoveries, new knowledge—even before the eighteenth century all these factors were under way. Then a new factor entered which has played a powerful part in substituting a progressive for a static world: new social hopes. The medieval age had no expectation of a better social life on earth. Charity was common but it was purely individual and remedial; it did not seek to understand or to cure the causes of social maladjustment; it was sustained by no expectation of better conditions among men; it was valued because of the giver's unselfishness rather than because of the recipient's gain, and in consequence it was for the most part unregulated alms-giving, piously motived but inefficiently managed. In the eighteenth century a new outlook and hope emerged. If man could pioneer new lands, learn new truth and make new inventions, why could he not devise new social systems where human life would be freed from the miseries of misgovernment and oppression? With that question at last definitely rising, the long line of social reformers began which stretched from Abbé de Saint-Pierre to the latest believer in the possibility of a more decent and salutary social life for human-kind. The coming of democracy in government incalculably stimulated the influence of this social hope, for with the old static forms of absolute autocracy now broken up, with power in the hands of the people to seek as they would "life, liberty and the pursuit of happiness," who could put limits to the possibilities? The medieval age was gone; the modern age had come, and its distinctive note was progress, with new inventions, new discoveries, new knowledge and new social hope.

It would be a fascinating task to watch these interweaving factors at their work and to trace their commingled influence as slowly their involved significance became clear, now to this man and now to that. The best narrative that has been written yet of this epochal movement is contained in Professor Bury's volume on "The Idea of Progress." There one sees the stream of this progressive conception of life pushing its way out as through a delta by way of many minds, often far separated yet flowing with the same water. Some men attacked the ancients and by comparison praised the modern time as Perrault did with "The Age of Louis the Great"; some men foresaw so clearly the possibility of man's control over nature that they dreamed of terrestrial Utopias as Francis Bacon did in "New Atlantis"; some men, like Descartes, sought to grasp the intellectual conditions of human improvement; and others, like Condorcet, became the fervid prophets of human perfectibility; some, like Turgot, re-examined history in terms of the new ideas; and some, like Saint Simon and Comte, sought to discover the law by which all progress moves. This new idea of life and history came "by divers portions and in divers manners," but no one can doubt its arrival. The life of man upon this earth was no longer conceived as static; it was progressive and the possibilities that lay ahead made all the achievements of the past seem like the play of childhood.

At last, in the nineteenth century, the climactic factor was added which gathered up all the rest and embraced them in a comprehensive philosophy of life. Evolution became a credible truth. No longer a dim conjecture, it was established in biology, and then it spread its influence out into every area of human thought until all history was conceived in genetic terms and all the sciences were founded upon the evolutionary idea. Growth became recognized as the fundamental law of life. Nothing in the universe without, or in man's life within, could longer be conceived as having sprung full-statured, like Minerva from the head of Jove. All things achieved maturity by gradual processes. The world itself had thus come into being, not artificially nailed together like a box, but growing like a tree, putting forth ever new branches and new leaves. When this idea had firmly grasped the human mind, the modern age had come indeed, and progress was its distinctive category of understanding and its exhilarating phrasing of human hope. Then came the days of mid-Victorian optimism with songs like this upon men's lips:

  "Every tiger madness muzzled, every serpent passion kill'd,
  Every grim ravine a garden, every blazing desert till'd,

  "Robed in universal harvest up to either pole she smiles,
  Universal ocean softly washing all her warless isles." [11]

IV

Any one, however, who has lived with discerning thought through the opening years of the twentieth century, must be aware that something has happened to chasten and subdue these wildly enthusiastic hopes of the mid-Victorian age. Others beside the "gloomy dean" of St. Paul's, whether through well-considered thought or through the psychological shock of the Great War, have come to look upon this rash, unmitigated enthusiasm about the earth's future as a fool's paradise. At any rate, no treatment of the idea of progress would be complete which did not dwell upon the limitations to that idea, now definitely obvious to thoughtful men.

As early as 1879, in Saporta's "Le Monde des Plantes," we run upon one serious setback to unqualified expectations of progress. Men began to take into account the fact that this earth is not a permanent affair. "We recognize from this point of view as from others," wrote Saporta, "that the world was once young; then adolescent; that it has even passed the age of maturity; man has come late, when a beginning of physical decadence had struck the globe, his domain." [12] Here is a fact to give enthusiasm over earthly progress serious pause. This earth, once uninhabitable, will be uninhabitable again. If not by wholesale catastrophe, then by the slow wearing down of the sun's heat, already passed its climacteric, this planet, the transient theatre of the human drama, will be no longer the scene of man's activity, but as cold as the moon, or as hot as colliding