It is not, then, because it was enlarged during the Renaissance into a fully thought out world-view that world- and life-affirmation made good its position in the modern age. If it was able to hold out right into the eighteenth century, when it triumphs against the world- and life-denial which mediæval thought and Christianity kept working in opposition to it, it owed this to the circumstance that progress in knowledge and power never ceased. In them the new mentality had a support which never gave way, but became continually stronger. Since the new scientific knowledge cannot be suppressed nor its progress arrested, belief in the power of truth becomes firmly established. Since it becomes more and more evident that nature works with a uniformity which never misses its aim, there grows up a confidence that the circumstances of society and of mankind generally can be so organized as to secure definite objects. Since man is ever obtaining [pg 063] greater power over nature, he takes it more and more as self-evident that the reaching of perfection in other spheres also is only a question of a sufficiency of will-power and a correct way of grappling with problems. Under the steadily working influence of the new mentality the world-view of Christianity changes, and becomes leavened with the leaven of world- and life-affirmation. It gradually begins to be accepted as self-evident that the spirit of Jesus does not give up the world in despair, but aims at transforming it. The early Christian conception of the Kingdom of God, which was born of pessimism and, thanks to Augustine, prevailed through the Middle Ages, is rendered impotent, and its place is taken by one which is the offspring of modern optimism. This new orientation of the Christian world-view, which is accomplished by a slow and often interrupted process of change between the fifteenth century and the end of the eighteenth, is the decisive spiritual event of the modern age. During this period Christianity takes no account of what is happening to itself. It believes that it is remaining unchanged, whereas in reality, by this change from pessimism to optimism, it is surrendering its original character. The man of modern times, then, becomes optimistic, not because deepened thought has made him understand the world in the sense of world- and life-affirmation, but because discovery and invention have given him power over it. This enhancement of his self-appreciation and the consequent strengthening of his will and his hopes, determine his will-to-live in a correspondingly pronounced and positive sense.