Early theorists

Giorgio Vasari
Giorgio Vasari's opinions about the "art" of creating art come through in his praise of fellow artists in the great book that lay behind this frontispiece: he believed that excellence in painting demanded refinement, richness of invention (invenzione), expressed through virtuoso technique (maniera), and wit and study that appeared in the finished work, all criteria that emphasized the artist's intellect and the patron's sensibility. The artist was now no longer just a craftsman member of a local Guild of St Luke. Now he took his place at court with scholars, poets, and humanists, in a climate that fostered an appreciation for elegance and complexity. The coat-of-arms of Vasari's Medici patrons appear at the top of his portrait, quite as if they were the artist's own.
The framing of the engraved frontispiece to Mannerist artist Giorgio Vasari's Lives of the Artists would be called "Jacobean" in an English-speaking context. In it, Michelangelo's Medici tombs inspire the anti-architectural "architectural" features at the top, the papery pierced frame, the satyr nudes at the base. In the vignette of Florence at the base, papery or vellum-like material is cut and stretched and scrolled into a cartouche (cartoccia). The design is self-conscious, overcharged with rich, artificially "natural" detail in physically improbable juxtapositions of jarring scale changes, overwhelming as a mere frame: Mannerist.
Gian Paolo Lomazzo
Another literary source from the period is Gian Paolo Lomazzo, who produced two works—one practical and one metaphysical—that helped define the Mannerist artist's self-conscious relation to his art. His Trattato dell'arte della pittura, scoltura et architettura (Milan, 1584) is in part a guide to contemporary concepts of decorum, which the Renaissance inherited in part from Antiquity but Mannerism elaborated upon. Lomazzo's systematic codification of aesthetics, which typifies the more formalized and academic approaches typical of the later 16th century, controlled a consonance between the functions of interiors and the kinds of painted and sculpted decors that would be suitable. Iconography, often convoluted and abstruse, is a more prominent element in the Mannerist styles. His less practical and more metaphysical Idea del tempio della pittura ("The ideal temple of painting", Milan, 1590) offers a description along the lines of the "four temperaments" theory of the human nature and personality, containing the ex