In characterising the original authors, apart from critics and commentators, whom Italy produced during the first half of the fifteenth century, we have omitted the men who really exerted the most important influence upon literature. These form a group by themselves--not one of Italian authors, for they rarely wrote in the vernacular; scarcely one of authors at all, for they worked chiefly as philologers. They are, however, much too important to be passed over without notice, representing as they did the Renaissance in its aspect as the rebirth of free thought and inquiry, a resurrection no less momentous than the revival of art and letters, and preparing the literary development which they were unable to effect. Few of them were men of extraordinary mental power, but all were passionate for the study of antiquity, and while, perhaps, intending to restore Latin to its rank as the sole literary language, set forces at work which deprived it of this primacy for ever. Even though Lorenzo de’ Medici might apologise for writing in a language condemned by men of good judgment, and Varchi’s schoolmaster might punish him for reading Petrarch, when men like Alberti took to cultivating the vernacular speech in emulation of the Latin, it was clear that the latter had already lost its monopoly. The humanists had nevertheless in their own domain the great advantage of being first in the field. They could hardly advance in any direction without initiating some movement momentous in its effect upon culture. Emanuel Chrysoloras brought the Greek language to Florence; his son-in-law, Filelfo, voyaged to Constantinople, and returned with a Greek library. Poggio Bracciolini, a most elegant Latinist and epistolographer--unfortunately best remembered by his virulent invectives, and by a book of facetiæ which does more credit to his gaiety than to his morals--rendered the greatest service by his assiduity in the collection of manuscripts. Leonardo Bruni accomplished even more by the simple step of making accurate translations of Plato and Aristotle, and thus delivering Western science from bondage to the Arabians, through whose paraphrases these writings had hitherto been chiefly known. Lorenzo Valla, an acute and intrepid critic and original thinker, enthusiastic for truth in the abstract, but not generally actuated by high principle, became the father of modern negative criticism by his overthrow of the scandalous Papal imposture of the Donation of Constantine. Gemistus Pletho, though a visionary, introduced Plato to Italy, and powerfully stimulated thought through the controversies aroused by his writings. Flavio Biondo was the first scientific archæologist, describing the monuments of pagan and Christian Rome, and investigating the topography of ancient Italy. Vittorino da Feltre showed practically by his school at Mantua what education ought to be, and Vespasiano da Bisticci wrote the lives of his fellows.