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PREFATIONE.

Nazianzenus Gregory of Nazianzus, 4th-century theologian praised his tutor, the great Basil, without end, for he was very skilled in Astronomy, Arithmetic, Geometry, and the other Mathematical sciences. These were taught to children with their milk, not without the greatest consideration: knowing that they do not only awaken the intellect to the speculation of the highest things, but are a ladder to the acquisition of other liberal arts, which cannot be perfectly learned by us without them. And this was the occasion that incited Plato to forbid entry into his school to anyone who ignored Geometry. Hence, he had written with clear letters above the door of that place: Let no one who is not a Geometer enter. Thus, to this purpose, Xenocrates the Chalcedonian chased away one unskilled in Geometry, saying to him, "Go with God, for you do not have the supports of Philosophy." And Plato in the Philebus dared to affirm that without the Mathematics, all other sciences were vain. He commanded in the sixth book of his Republic that the Mathematics be learned before all other sciences: as those that not only facilitate the path for us to understand the other liberal faculties, but reveal to us the way to know how to rightly administer the Republic. And in the seventh book of the same, Plato similarly had to say that just as the eye of our intellect is obscured by the studies of other sciences, so by those of the Mathematics is it recreated and restored, due to the sweetness that the soul feels in their contemplation. I, therefore, who by the great favor of Heaven have spent almost all the flower of my years in the honored service of the most happy memory of the never-sufficiently-praised Lord, the most illustrious and excellent Marquis of Marignano, great Conductor of war, nay, the right arm of that magnanimous and most invincible Emperor Charles V, who was in his day, as the East and the West well know, by sea and by land, a tremendous and formidable thunderbolt of arms; and having been raised and exercised for a long time under the observance and incomparable virtue of this glorious Cavalier, in whom (to say nothing of others) shone forth among his many divine gifts and qualities, with supreme valor and judgment, the supreme light of military art, I have endeavored with every study and dili-