There are so many things in the Works of _Vitruvius_ that do not directly appertain to Architecture, that one would think they were less fitted to Instruct those that have a design to learn the Precepts of this Art, than to perswade the World that the Author was the most knowing Architect that ever was, and a Person of the greatest Merit: He had the Honour to serve _Julius Caesar_ and _Augustus_, the two Greatest and most Magnificent Princes of the World, in an Age when all things were come to the highest degree of Perfection. [Sidenote: _Lib. 6. Preface._] For one may see in reading his Works, which are full of a wonderful variety of Matters, which he treats of with a singular Erudition, that this great Man had acquired that Profound Knowledge which is necessary for his Profession by more excellent Methods, and more capable of producing something excellent, than the bare exercise and ordinary practice of a Mechanical Art could possibly do; being compleat in all the Liberal Arts and Sciences, and his great Wit being accustomed, even from his Cradle, to understand the most difficult Matters: He had acquired a certain Facility which meer Artizans have not, of penetrating the deepest Secrets, and all the difficulties of so vast an Art, as that of Architecture. [Sidenote: _Lib. 2. Pref._] [Sidenote: _Lib. 6. Pref._] Now as it's true that in the Practice and Exercise of Arts, one does not always easily distinguish the Abilities of those that work in them. The great Capacity of _Vitruvius_ before the publishing of his Book, which he Composed when he was in Years, had not all the Esteem it deserved; which he complains of in his Preface, and in the Age he lived; though it was full of the most refined Wits, yet he had the fortune of others, to find few to defend him from the Surprizes and Attacks of false Reasoning, and from the injustice that prejudice creates, to those who apply themselves more to cultivate the Talents they possess, than to make parade of them. [Sidenote: _Lib. 2. Pref._] [Sidenote: _Lib. 6. Pref._] [Sidenote: _Lib. 3. pref_.] [Sidenote: _Lib. 3. Pref_.] [Sidenote: _Lib. 6. Pref_.]