Here are Three Things which ought to meet in every Fabrick, viz. Solidity, Convenience and Beauty, which Architecture gives them; by the due ordering and disposition of all the Parts that compose the Edifice, and which she rules by a just Proportion, having regard to a true Decorum, and well regulated Oeconomy; from whence it follows, that Architecture has Eight Parts, viz. Solidity, Convenience, Beauty, Order, Disposition, Decorum, Oeconomy.
Solidity depends upon the goodness of the Foundation, choice of Materials, and the right use of them; which ought to be with a due order, disposition and convenient Proportion of all Parts together, and of one in respect of another.
Convenience likewise consists in the ordering and disposition, which is so good that nothing hinders the use of any part of the Edifice.
Beauty consists in the excellent and agreeable form, and the just proportion of all its parts.
Order is that which makes, that all the parts of an Edifice have a convenient bigness, whether we consider them apart or with Relation to the whole.
Disposition is the orderly Ranging and agreeable Union of all the parts that compose the Work; so that as Order respects the Greatness, Disposition respects Form and Situation, which are Two Things compriz'd under the word Quality, which Vitruvius attributes to Disposition, and opposes to Quantity, which appertains to Order. There are three ways by which the Architect may take a view beforehand of the Fabrick he is to build, viz. First, Ichnography, which is the Geometrical Plan; Orthography, which is the Geometrical Elevation, and Scenography, which is Perspective Elevation.
Proportion, which is also call'd Eurythmy, is that which makes the Union of all parts of the Work, and which renders the Prospect agreeable, when the Height answers the Breadth, and the Breadth the Length; every one having its just measure. It is defin'd, the Relation that all the Work has with its Parts, and which every one of them has separately to the Idea of the whole, according to the measure of any Part. For as in Humane Bodies there is a Relation between the Foot, Hand, Finger and other Parts; so amongst Works that are Perfect, from any particular Part, we may make a certain Judgment of the Greatness of the whole Work: For Example, the Diameter of a Pillar, or the Length of a Triglyph, creates in us a right Judgment of the Greatness of the whole Temple.
And here we must remark, that to express the Relation that many things have one to another, as to their Greatness or different Number of Parts, Vitruvius indifferently makes use of three words, which are Proportion, Eurythmy and Symmetry. But we have thought it proper only to make use of the word Proportion, because Eurythmy is a Greek word, which signifies nothing else but Proportion; and Symmetry, although a word commonly used, does not signifie in the Vulgar Languages what Vitruvius understands by Proportion; for he understands by Proportion, a Relation according to Reason; and Symmetry, in the vulgar Languages, signifies only, a Relation of Parity and Equality. For the word Simmetria signifies in Latin and Greek Relation only. As for Example, as the Relation that Windows of Eight Foot high, have with other Windows of Six Foot, when the one are Four Foot broad, and the other Three: and Symmetry, in the Vulgar Languages, signifies the Relation, for Example, That Windows have one to another, when they are all of an equal height and equal breadth; and that their Number and Distances are equal to the Right and the Left; so that if the distances be unequal of one side, the like inequality is to be found in the other.
Decorum or Decency, is that which makes the Aspect of the Fabrick so correct, that there is nothing that is not approv'd of, and founded upon some Authority. It teaches us to have regard to three things, which are, Design, Custom and Nature.
The Regard to Design makes us chuse for Example, other Dispositions and Propertions for a Palace than for a Church.