During the 14th century, humanism strengthened, diversified, and spread, with Florence remaining at its epicentre. The three figures who were most critical to the rise of the humanist movement during this period were Petrarch (Francesco Petrarca), Giovanni Boccaccio, and Coluccio Salutati.

The influence of Petrarch was profound and multifaceted. He promoted the recovery and transcription of Classical texts, providing the impetus for the important Classical researches of Boccaccio and Salutati. He threw himself into controversies in which he defined a new humanism in contradistinction to what he considered to be the barbaric influence of medieval tradition. He carried on an energetic correspondence that established him as a cultural focal point and would provide, even if all his other works were lost, an accurate index of his views and their development. As a theologian (he was an ordained priest) he advanced the view, held by many humanists who followed, that Classical learning and Christian spirituality were not only compatible but also mutually fulfilling. As a political apologist, he gave hearty support to Cola di Rienzo’s brief revival of the Roman Republic (1347). As a poet, he was the first Renaissance writer to produce a Latin epic (Africa), but he was even more important for his compositions in the vernacular. His Canzoniere provided the model on which the Renaissance lyric was to take shape and the standard by which future works would be judged. His work established secular poetry as a serious and noble pursuit. His eloquent and forceful presence made him a personal symbol of his own ideas. Crowned with laurel, favoured by rulers, legates, and scholars, he became the human focus for the new interest in Classical revival and literary artistry.

It was, however, as a philosophical spokesman that Petrarch exerted his greatest influence on the history of humanism. In his prose works and letters he established positions that would be central to the movement, and he broached issues that would be its favourite subjects for debate. His idea of the poet as a philosophical teacher and thus as a champion of culture would inspire humanists from Boccaccio to Sir Philip Sidney (1554–86). His endorsement of the study of rhetoric and his underlying notion of language as an informing principle of the individual and society would become crucial subjects of humanistic discussion and debate. His view of Classical culture, not as an isolated element of the past but as an authentic alternative to his own medieval society, was of equal historical importance. He helped to reestablish the Socratic tradition in Europe by specifying self-knowledge as a primary goal of philosophy. This attitude and his unfailing insistence on moral autonomy were early and important signs of the individualism that would become a Renaissance hallmark. He emphasized human virtue as opposed to fortune and thus set the stage for numerous famous treatments of this theme. He struggled repeatedly with the dilemma of action versus contemplation, establishing it as a favourite topic for humanistic debate. Petrarch did not invent these subjects, nor does he usually treat them with overwhelming power; his achievement lies in the energy and commitment with which he made his work their forum.

A friend and devoted supporter of Petrarch, Giovanni Boccaccio created an opus that was equally revolutionary. His Teseide was the first classical epic to have been written in the vernacular, and it influenced the Italian epics of Ariosto and Tasso. His De genealogia deorum gentilium (“On the Genealogy of the Gods of the Gentiles”), a scholarly interpretive compendium of classical myth, was the first in a long line of Renaissance mythographies; it includes a celebrated defense of poetry as a medium of hidden truth, a stimulant to virtue, and a source of mental health. He worked in support of his city during the troubled times that led up to the War of the Eight Saints against the Avignon papacy (1309–77). His prose style would become a benchmark for Italian expression in the Renaissance. His most memorable contribution to humanism, however, is probably the famous Decameron. Ostensibly this work is no more than a collection of 100 tales about love, but subjected to the interpretive scrutiny that Boccaccio himself recommends in De genealogia deorum gentilium, the Decameron takes on a far more serious tone. The opening phrase “Umana cosa è” (“It is a human thing”) is deeply thematic, signaling the socially conscious tone of the stories to come. Through moral fable and direct address to the reader, he undertakes a reinterpretation of human experience based not on received doctrine but rather on perceived reality. Appealing repeatedly to reason and nature, and constantly implying the superiority of awareness to innocence (which he equates with ignorance), he declares war on institutional tyrannies of church and state, calling instead for a moral order built fairly and solidly on the potentialities of human nature. His 10 storytellers, who leave the plague-ravaged and chaotic city of Florence and reestablish themselves at delightfully landscaped villas, suggest the remaking of culture through disentanglement with the past, unprejudiced analysis, and enlightened imagination. Rightly considered to be the wellspring of Western realism, the Decameron is also a monument to humanism. Although it makes little mention of Classical thought, Boccaccio’s great work rings with a tone that was even more basic to the humanistic movement: an emphasis on the human capacity for self-knowledge and willed renewal.

Like Petrarch and Boccaccio, Coluccio Salutati collected manuscripts, wrote on morality and politics, and carried on a voluminous correspondence. He was an aggressive and scientific philologist, instrumental in establishing principles of textual criticism that would become key elements of the humanistic method. He was a forceful apologist for the active life, and his theories bore fruit in his own career as chancellor of the Florentine republic. His use of classical eloquence in the service of his state was an early documentation of the humanistic faith in the political power of rhetoric; it led a bitter enemy, Gian Galeazzo Visconti of Milan, to say that a thousand Florentine horsemen had hurt him less than the letters of Coluccio. Salutati was succeeded in the Florentine chancellorship by two scholar-statesmen who reflected his influence: Leonardo Bruni (1369–1444) and then Gian Francesco Poggio Braccioloni (1380–1459). Bruni was a pioneer in the advocacy of humanistic education, holding that the studia humanitatis shape the perfected man and that the goal of this perfected virtue is political action. His theory of education stressed the importance of practical experience (implicit in the work of Boccaccio) and put heavy emphasis on historical studies. His history of Florence is considered to be the first work of modern historiography; and, under the influence ofManuel Chrysoloras (1368–1415), a Byzantine teacher who had lectured at Florence and Pavia, he produced Latin translations of Plato and Aristotle that broke with medieval tradition by reproducing the sense of the Greek prose rather than following it word by word. Poggio, the foremost recoverer of Classical texts, was also a moralist, a historian, a brilliant correspondent, and an early scholar of architectural antiquities. His long career, which included service to both church and state and friendships with Salutati, Bruni, Niccolò Niccoli, Guarino, Nicholas of Cusa, Donatello, and Cosimo de’ Medici, exemplifies the scope and vitality of Italian humanism. Together these Florentine chancellors, whose active lives spanned almost a century, strengthened and consolidated the humanistic program. Moreover, their leadership strongly influenced the cultural developments that would make 15th-century Florence the most active intellectual and artistic centre in Europe.

As one proceeds with the history of humanism, the following major points about its development in the 13th and 14th centuries ought to be kept in mind. Humanism received its crucial imprint from the work of a single man and thence developed among men who maintained close touch with each other and acknowledged a shared mission. Humanism was not originally an academic movement but rather a program defined and promoted by statesmen and men of letters. Its proclaimed goal was widespread civic and cultural renewal; therefore, it chose its subjects for consideration from the phenomena of human life as lived and adopted the Ciceronian model of philosopher as citizen, in preference to the contemplative ideal. The heavy emphasis on civic action is connected with the fact that humanism developed in a republic rather than in a monarchy.