As a painter, Leonardo da Vinci believed one needed synesthesia and associative perception. When we were little, we would look at clouds in the sky and imagine what they resembled. Though, in adults' eyes, those clouds had nothing to do with what children described and instead foretold an approaching storm.
The damp marks on the wall had no meaning in themselves. Yet after a painter stared at them, synesthesia and associations between neurons gave rise to imagination. During that process, the brain swiftly found images stored within it that resembled the damp marks. Figures, landscapes, and animals were filtered out from memory, and the brain transmitted its matches to the cognitive regions. The concept of a "portrait" was confirmed, and the meaningless water stains became a human figure in the painter's eyes.
"Leonardo's Knot" had been inlaid into the wall with colored stones. Unlike tempera paintings, it would not peel away from dampness.
It was a perfect circle, reminding Georgiana of the rose windows in Gothic churches. It was also called a Catherine Window, named after Saint Catherine, who had suffered execution on the wheel.
Kant had also discussed "common sense," usually in relation to judgments of taste. Kant called such judgments "reflective taste," while the opposite was "sensory taste." Sensory taste offered only a private judgment, whereas reflective taste supposedly made a universal judgment, one that went beyond an individual's private feelings.
A thousand readers saw a thousand Hamlets. Leonardo da Vinci might simply have wanted to group Old Jacob, Peter, and John together. Old Jacob's gesture was the same as Peter's, and both pointed in the same direction—at John.
Likewise, rosettes were often used to decorate church floors and were very popular in Roman architecture. These rosettes did not form the shape of a rose on the floor.