Ars Magna offered the first published, systematic exposition of solving cubic and quartic equations. The milestone is central to the history of algebra, but authorship is tangled: Cardano based the cubic method on the work of Scipione del Ferro and Niccolò Tartaglia — with whom he had a bitter public dispute — while Ludovico Ferrari independently solved the quartic within Cardano's circle. It is the most famous case of complex credit in Renaissance mathematics.