The publishing of the Ars magna was an extraordinary event in the history of polynomial equations. After long ages when every new treatise was either a compendium of previous knowledge or a very modest original contribution to algebra, the Ars Magna contained mostly totally new discoveries: in fact apart from a brief chapter concerned with linear and quadratic equations the rest of the book is dedicated to all the different types of cubics and of quartics. The method of solving the quartic had been discovered by Luigi Ferrari, a disciple of Cardano, ``under my request" as Cardano wrote in the introduction to the book.