The most important, in connection with its influence and consequences, of the discoveries made by scholars concerning the fraudulent character of historic documents, occurred as late as the beginning of the fifteenth century. It was about 1440 when Laurentius Valla, at that time acting as secretary for King Alphonso of Naples, wrote his report upon the famous _Donation_ of Constantine, the document upon which the Roman Church had for nearly a thousand years based its claims to be the direct representative in Western Europe of the old imperial authority. Valla brought down upon his head much ecclesiastical denunciation. The evidences produced by him of the fact that the document had been fabricated a century or more after the death of Constantine could not be gotten rid of, and, although for a number of years the Church continued to maintain the sacred character of the _Donation_, and has, in fact, never formally admitted that it was fraudulent, it was impossible, after the beginning of the sixteenth century, even for the ecclesiastics themselves to base any further claims for the authority of the Church upon this discredited parchment. Of almost equal importance was the discovery of the fabrication of the pseudo Isidoric _Decretals_. The _Decretals_ had been concocted early in the ninth century by certain priests in the West Frankish Church, and had been eagerly accepted by Pope Nicholas I., who retained in the archives of the Vatican the so-called originals. The conclusion that the _Decretals_ had been fraudulently imposed upon the Church was not finally accepted until the beginning of the fourteenth century. It was with the humanistic movement of the Renaissance that historical criticism had its birth, and a very important portion of the work of such criticism consisted in the analysis of the lack of foundation of a large number of fabulous legends upon which many of the claims of the Church had been based.