What has pleased, and continues to please, is likely to please again: hence are derived the rules of art, and on this immoveable foundation they must… - Joshua Reynolds

A painter must not only be of necessity an imitator of the works of nature...but he must be as necessarily an imitator of the works of other painters: this appears more humiliating, but is equally true; and no man can be an artist, whatever he may suppose, upon any other terms.

No Art can be grafted with success on another art. For though they all profess the same origin, and to proceed from the same stock, yet each has its own peculiar modes both of imitating nature, and of deviating from it, each for the accomplishment of its own particular purpose. These deviations, more especially, will not bear transplantation to another soil.

As the natural dignity of the subject(of a portrait)is less, the more the ornamental helps are necessary to its embellishments.