This is an edition of one of the crucial texts of Renaissance skepticism, Quod nihil scitur, by the Portuguese scholar Franciso Sanches. The treatise, first published in 1581, is a refutation of Aaristotelian dialectics and scientific theory in the search for a true scientific method. This volume provides a critical edition of the original text, an English translation (the first ever published), a substantial introduction, and comprehensive annotation.