Rules · Theory · Proportion
Distinguish positive beauty, which pleases everyone for evident reasons (fine materials, size, precise workmanship, symmetry), from arbitrary beauty, which pleases through custom, including the exact proportions of the orders.
Perrault pointed out that the Pantheon, the Theatre of Marcellus and the Colosseum all use different proportions for the same order, and yet all are admired. If proportions were natural laws like musical consonances, he argued, the ancients would have agreed.
To find how thick the pier of an arch must be, divide the intrados into three equal parts; draw a line from the springing through the first division, and produce it beyond the springing by its own length. A vertical through the end of that line marks the outer face of the pier.
pier ≈ ¼ span (semicircle) · ≈ 0.23 span (equilateral) · less for a lancet
To unify a façade of two or more storeys, run a single order of pilasters or columns through all of them, from the base to the main cornice.
Proportion every step so that twice its height plus its depth equals the length of a natural pace on the level: two feet, or 24 pouces.
2 r + g = 24 pouces ≈ 65 cm (modern practice: 60–66 cm)
Hold that the beauty of the orders comes from fixed proportions that please by nature, as consonances do in music; where the ancients differ, the differences answer to circumstances such as distance and height.
Give the flight of steps before a temple an odd number, so that one who starts with the right foot will also set the right foot first on the top.
Make the parterre oblong rather than square, since figures somewhat oblong look better on the ground than square ones; later practice made it as broad as the front of the house and about twice as long.
parterre oblong; later practice: width ≈ house front, length ≈ 2 × width
Cite this page Chris Paton, “Positive and arbitrary beauty”, The Textbook of Architecture, https://textbookofarchitecture.com/rule/perrault-arbitrary-beauty. Text, drawings and models licensed under CC BY-NC 4.0.