An Answer to the Objection made about the Point of Sight in Perspective.
Every one does not approve, that in a Perspective of great Extent one Point of Sight only should be assign’d the whole Work; as for Example, In the whole Length of the Nave, Cupola, and Tribune, express’d in the Ninety-third Figure, they will by no means allow of one single Point, but insist upon several.
I answer, This Objection may be understood two ways; either that one Point alone is not sufficient for that whole Length, and in this sense ’tis true; for that Space being very long, it ought to be divided into Parts, and proper Points assign’d to the Tribune, Cupola, and Vault of the Nave; as is commonly taught, where the Situation is of a great Length, and not very high. Or it may be understood of any One of the said Parts, and so is altogether false. First, Because in the Vaults of Halls or Churches painted by the greatest Masters, if they consist of one Piece only, we find but one Point of Sight assign’d. Secondly, Since Perspective is but a Counterfeiting of the Truth, the Painter is not oblig’d to make it appear real when seen from Any part, but from One determinate Point only. Thirdly, Because, if in a Vault, for Example, where you would paint one entire Design of Architecture and Figures, you assign several Points of Sight, you will find no place whence you may take a perfect View of the Whole, and at best you can only view each Part from its proper Point. From all which Reasons I conclude, that the Introduction of many Points into the same Piece, is more injurious to the Work, than making use of one only: Wherefore ’tis absolutely necessary in a regular Situation, and where the Work is all of a piece, so to place the same, as that the Figures and Architecture may from every part of the Design have respect thereto. This suppos’d, I confess that I myself make use of one Point of Sight only, in very large Vaults that consist of one Design, such as that of the Nave of the Church of S. Ignatius. If therefore through the Irregularity of the Place, the Architecture appear with some Deformity, and the Figures intermix’d therewith seem any thing lame and imperfect when view’d out of the proper Point, besides the Reasons just now given, it’s so far from being a Fault, that I look upon it as an Excellency in the Work, that when view’d from the Point determin’d, it appear, with due Proportion, streight, flat, or concave; when in reality it is not so.