This project aspires to provide a synthesis of quattrocento Italian humanist theories of how history should be written. This is the period when historical writing was reoriented according to classical models, classified as a species of rhetoric, codified as a literary endeavor, and endowed with a moral purpose. It is also the period when humanists became convinced that there was a definite method, an ars, for writing history. My goal is to explain why and how this happened, as well as to trace the historiographical theories and models developed by humanists throughout the fifteenth century. Departing from previous attempts to distill a humanist theory of historiography from actual works of history, I will explore a group of relatively neglected and undervalued theoretical sources dealing specifically with the ars historica—sources of great importance for both the early modern and the modern craft of history.