So far the outside only of Petrarch's instinct for humanism has been touched. How fully he possessed its large and liberal spirit is shown by the untiring war he carried on against formalism, tradition, pedantry, and superstition. Whatever might impede the free play of the intellect aroused his bitterest hatred. Against the narrow views of scholastic theologians, against the futile preoccupations of the Middle-Age materialists, against the lawyers and physicians and astrologers in vogue, he declared inexorable hostility.[24] These men, by their puerilities and falsities, obstructed the natural action of the mind; therefore Petrarch attacked them. At the same time he recognised the liberators of the reason by a kind of tact. Though he could not interpret the sixteen dialogues of Plato he possessed in Greek, he perceived intuitively that Plato, as opposed to Aristotle, would become the saint of liberal philosophy, surveyed by him as in a Pisgah-view. His enthusiasm for Cicero and Virgil was twofold; in both respects he proved how capable he was of moulding the taste and directing the mental force of his successors. As an artist, he discerned in their style the harmonies of sound and the proprieties of diction, whereby Latin might once again become the language of fine thoughts and delicate emotions. As a champion of intellectual independence, he saw that, studying their large discourse of all things which the reason and imagination can appropriate, the thinkers of the modern age might shake off scholastic fetters, and enter into the inheritance of spiritual freedom. Poetry and rhetoric he regarded not merely as the fine arts of literature, but as two chief instruments whereby the man of genius arrives at self-expression, perpetuates the qualities of his own soul, and impresses his character upon the age. Since this realisation of the individual in a high and puissant work of art appeared to him the noblest aim of man on earth, it followed that the inspired speech of the poet and the eloquence of the orator became for Petrarch the summit of ambition, the two-peaked Parnassus he struggled through his lifetime to ascend.[25] The ideal was literary; but literature implied for Petrarch more than words and phrases. It was not enough to make melodious verse, or to move an audience with well-sounding periods. The hexameters of the epic and the paragraphs of the oration had to contain solid thought, to be the genuine outcome of the poet's or the rhetorician's soul. The writer was bound to be a preacher, to discover truth, and make the truths he found agreeable to the world.[26] His life, moreover, ought to be in perfect harmony with all he sought to teach.[27] Upon the purity of his enthusiasm, the sincerity of his inspiration, depended the future well-being of the world for which he laboured.[28] Thus for this one man at least the art of letters was a priesthood; and the earnestness of his vocation made him fit to be the master of succeeding ages. It