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that is, numeration and measurement, termed arithmetic and geometry, which treat with thehighest truth of the discontinued and continuedquantity.

Here there will be no dispute as to

whether twice three make more or less than six, nor whether two angles of a triangle are less than two right angles, but eternal silence shall ignorere all controversy, and the devotees of the true science will finish their studies in peace, which the lying mental sciences cannot do.

And if thou sayest that true and established science of this kind is a species of mechanics, because they can only be completed by the hand, I will say the same of all the arts, such as that which passes through the hand of the sculptor, which is a kind of drawing, a part of painting; and astrology and the other sciences pass through manual operation, but they are mental in the first place, as painting, which first of all exists in the mind of the composer, and cannot attain to fulfilment without manual labour. With regard to painting, its true and scientific principles must be established: what constitutes a shaded body, what constitutes a primary shade, a derivative shade, what constitutes light: that is, darkness, light, colour, size, shape, position, distance, propinquity, motion, rest, which are comprehended by the mind only, and without manual labour.

And this is the science of painting which remains in the mind of those who meditate on it, from which

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