[11] And as you must know that it is common for there to be great preludes to great propositions, and the greatest of all propositions is virtue, for it is conversant about the most important of all materials, namely, about the universal life of man; very naturally, therefore, that will not employ any short preface, but rather it will use as such, grammar, geometry, astronomy, rhetoric, music, and all the other sorts of contemplation which proceed in accordance with reason; of which Hagar, the handmaid of Sarah, is an emblem, as we will proceed to show. [5] [6]