[*†54.] In the same manner, that bare practice, destitute of the lights of art, is always subject to fall into a precipice, like a blind traveller, without being {55.} able to produce any thing which contributes to a solid reputation; so the speculative part of painting, without the assistance of manual operation, can never attain to that perfection which is its object, but slothfully languishes as in a prison; for it was not with his tongue that Apelles performed his noble works. Therefore, {60.} though there are many things in painting, of which no precise rules are to be given, [*†61.] (because the greatest beauties cannot always be expressed for want of terms,) yet I shall not omit to give some precepts, which I have selected from among the most considerable which we have received from nature, that exact school-mistress, after having examined her most secret recesses, as well as [*†63.] those master-pieces of antiquity, which were the chief examples of this art; and it is by this means, that the mind and the natural disposition {65.} are to be cultivated, and that science perfects genius; [*†66.] and also moderates that fury of the fancy which cannot contain itself within the bounds of reason; but often carries a man into dangerous extremes. For there is a mean in all things; and certain limits or bounds wherein the good and the beautiful consist, and out of which they never can depart. [Sidenote: III. Concerning the subject.] This being premised, the next thing is to make choice of [*†69.] a subject beautiful and noble; which being of itself capable of all the charms and graces, {70.} that colours, and the elegance of design, can possibly give, shall afterwards afford, to a perfect and consummate art, an ample field of matter wherein to expatiate itself; to exert all its power, and to produce somewhat to the sight, which is excellent, judicious, [*†72.] and ingenious; and at the same time proper to instruct, and to enlighten the understanding. “At length I come to the work itself; and at {75.} first, find only a bare strained canvas, on which the sketch is to be disposed by the strength of a happy imagination;” [*†74.] which is what we properly call invention. [*†75.] [Sidenote: Invention the first part of painting.] [*†76.] Invention is a kind of muse, which, being possessed of the other advantages common to her sisters, and being warmed by the fire of Apollo, is raised higher than the rest, and shines with a more glorious and brighter flame. [Sidenote: IV. The disposition, or œconomy of the whole work.] [*†77.] It is the business of a painter, in his choice of attitudes, to foresee the effect and harmony of the lights and shadows, with the colours which are to enter into the whole; taking from each of them, that which will most conduce to the production of {80.} a beautiful effect. [Sidenote: V. The faithfulness of the subject.]