Lorenzo Ghiberti's unfinished Commentaries is the earliest surviving writing by a great artist about theprinciples and goals of art, about his own art, and about the attributes and means necessary for the artist toproduce excellent art.Part I of this study reevaluates the character and purpose of Ghiberti's book and examines its content, structure and organization, sources, dating, literary quality and style, and its place in the literature ofItalian art. It describes each of the book's three commentaries and shows how they are interrelated andtogether form a coherent whole. It discusses Ghiberti's deliberate selection of the excerpts from Latinancient and medieval texts that comprise most of the first and third commentaries and his selection of theartists and works recorded in the second commentary, and it explores the rationale behind these choices. While all three commentaries contribute to understanding Ghiberti's interests and intent, the secondcommentary is the fulcrum of his book and can be fully appreciated only in the context of his writing as awhole. At the same time, it is important in its own right as a key source of information on late thirteenth-and fourteenth-century Tuscan and Roman painting and sculpture and Ghiberti's art. Unlike the poorlytranslated, defective, and often incomprehensible excerpts in the first and third commentaries, the secondcommentary was written almost entirely in Ghiberti's own words and is easily understood. Part II presents a new transcription and annotated English translation of this primary document for thehistory of early Renaissance art and the history of art criticism.