[Sidenote: Natural periods merge into one another.] The date at which this transition in European life was made will doubtless be differently given according as the investigator changes his point of view. In truth, there is not in national life any real epoch, because there is nothing in reality abrupt. Events, however great or sudden, are consequences of preparations long ago made. In this there is a perfect parity between the course of national and that of individual life. In the individual, one state merges by imperceptible degrees into another, each in its beginning and end being altogether indistinct. No one can tell at what moment he ceased to be a child and became a boy--at what moment he ceased to be a youth and became a man. Each condition, examined at a suitable interval, exhibits characteristics perfectly distinctive, but, at their common point of contact, the two so overlap and blend that, like the intermingling of shadow and light, the beginning of one and end of the other may be very variously estimated. [Sidenote: Artificial epochs.] In individual life, since no precise natural epoch exists, society has found it expedient to establish an artificial one, as, for example, the twenty-first year. The exigencies of history may be satisfied by similar fictions. A classical critic would probably be justified in selecting for his purpose the foundation of Constantinople as the epoch of the commencement of the Age of Faith, and its capture by the Turks as the close. It must be admitted that a very large number of historical events stand in harmony with that arrangement. [Sidenote: Origin and end of the Age of Faith.] A political writer would perhaps be disposed to postpone the date of the latter epoch to that of the treaty of Westphalia, for from that time theological elements ceased to have a recognized force, Protestant, Catholic, Mohammedan, consorting promiscuously together in alliance or at war, according as temporary necessities might indicate. Besides these other artificial epochs might be assigned, each doubtless having advantages to recommend it to notice. But, after all, the chief peculiarity is obvious enough. It is the gradual decline of a system that had been in activity for many ages, and its gradual replacement by another. [Sidenote: Prelude to the Age of Reason.] As with the Age of Reason in Greece, so with the Age of Reason in Europe, there is a prelude marked by the gradual emergence of a sound philosophy; a true logic displaces the supernatural; experiment supersedes speculation. It is very interesting to trace the feeble beginnings of modern science in alchemy and natural magic in countries where no one could understand the writings of Alhazen or the Arabian philosophers. Out of many names of those who took part in this movement that might be mentioned there are some that deserve recollection.