The seventeenth century marked the emergence in Italy of a novel type of painted illusion: quadratura. Its practitioners created a new genre of art, with ceilings as its domain, which relied upon linear perspective and the real setting of the illusion to produce a sense of wonder in beholders and to persuade them of a rhetorical message. This thesis focuses on three illusionistic ceilings: the Apotheosis of Saint Clement, the Allegory of Divine Providence, and the Glorification of Saint Ignatius. In treating these works as varied manifestations of the same artistic and cultural milieu, this investigation produces a model, or foundational set of tools, with which to analyze the creation and reception of illusionistic ceilings of seventeenth-century Rome.