_Vitruvius_ was a Man, who, as to the exteriour, made a small Figure, and who had not heaped up great Riches by the practice of his Profession; and having, as it were, buried himself in study, and wholly given himself over to the Contemplation of Sciences, understood little of the Arts of the Court, or the Crafty Slights of pushing on his Fortune and making himself considerable; for though he was bestowed upon, and recommended to _Augustus_, by the Princess _Octavia_ his Sister, we cannot find that he was employed in any Works of great Importance. The Noblest Edifice that we can learn that _Augustus_ caused to be built, was, the Theatre of _Marcellus_; and this was done by another Architect: And the only Fabrick we can find he was employed in was not at _Rome_, but at _Fano_, a very little City; insomuch, that the greatest part of the Architects of that Age, who had gained the general Vogue, being so ignorant, that they did not know even (as himself is forced to declare) the first Principles of their Art: The Quality of a mere Architect was become so Contemptible, that if his Books had not carried all the Marks of an extraordinary Knowledge, and rare abilities, and undeceived the World by taking away the prejudice that his small employ created him, the Precepts he has left us would have wanted that Authority that was necessary to support them. For Architecture being an Art that has scarce any other Rule to walk by, in performing all those Excellencies her Works are capable of, than what we call a Good Fancy, which truly distinguishes that which is Beautiful and Good from that which is not so; it's absolutely necessary that one be perswaded that the Fancy he follows is better than any other; to the end, that this Perswasion insinuating it self into them that study this Art, it may form in them a Correct and Regular Idea, which without this Perswasion, would be always floating and uncertain; so that to establish this Good Fancy, it's necessary to have one to whom we give great deference, and who has merited great Credit by the Learning that is found in his Writings; and is believed to have had sufficient abilities of chusing well among all Antiquity, that which is most solid and capable of founding the Precepts of Architecture.