Which Science Is Mechanical; Experience the Mother of Certainty
True science is born of the senses and ends in demonstrated experience; where reason fails, shouting rules
Opening with the poet's 'feigned composite' that at best equals what Leonardo calls the weakest part of painting, this leaf turns to defining mechanical versus non-mechanical knowledge. He distinguishes the mechanical, born of experience, the scientific, born and ending in the mind, and the semi-mechanical, which begins in science and ends in manual operation, then insists that sciences not born of experience, the mother of all certainty, and not verified through the five senses are vain and full of error. Disputes over things beyond the senses, such as the essence of God and of the soul, breed only shouting, whereas true science has one sole conclusion that silences all argument. The true sciences are those that experience has made penetrate through the senses.
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The poet's feigned composite equals painting's weakest part
The poet, with borrowed matter, makes a lying or, more honestly, a feigned composite. In this free fiction the poet has made himself equal to the painter, which Leonardo calls the weakest part of painting.
Experience, mother of certainty, the test of true science
Leonardo divides knowledge into the mechanical, born of experience, the scientific, born and ending in the mind, and the semi-mechanical. He holds vain and full of error any science not born of experience, the mother of all certainty, whose origin, middle, or end does not pass through the five senses.
Where reason fails, shouting takes its place
Doubting even what passes through the senses, Leonardo doubts still more the things rebellious to them, such as the essence of God and of the soul, forever disputed. Where reason is lacking, shouting supplies, so that where there is shouting there is no true science, for truth has one sole conclusion that ends all dispute.