Al-Sijzī was a mathematician of the second half of the tenth century, a particularly fertile period for the history and philosophy of mathematics. He occupies a central place in a generation that, in particular, succeeded in renewing the methods of geometry and opening up new avenues of research in this field.

This book contains a critical edition of several of his writings on plane and solid geometry, thus enriching research in the history and philosophy of mathematics.

Al-Sijzī endeavours to identify the laws of geometry and, through a commentary on Euclid's books, to explain its principles. In the course of this work to elucidate the laws and concepts of the discipline, he also devoted essays to teaching, and others to the theory of demonstration. In addition, he kept up a rich correspondence with contemporary mathematicians, a living illustration of the mathematical research of his time.