s with no intention of
publishing them to the world. But his ideal of art depended
intimately, none the less, on the system he had thrown out seemingly in
so haphazard a manner. His method gives to his writings their only
unity. It was more than a method: it was a permanent expression of his
own life, which aided him to construct a philosophy of beauty
characteristic of the new age.

He had searched to find a scientific basis for art, and discovered it
in the imitation of nature, based on rational experience. This idea
was, in part, Aristotelian, imbibed with the spirit of the time; though
in the ordinary acceptance of the word Leonardo was no scholar, least
of all a humanist. His own innovation in aesthetic was in requiring a
rational and critical experience as a necessary {xiv} foundation, the
acquisition of which was to result from the permanent condition of the
mind. He had trained his own faculties to critically observe all
natural phenomena: first try by experience, and then demonstrate why
such experiment is forced to operate in the way it does, was his
advice. The eye, he gave as an instance, had been defined as one
thing; by experience, he had found it to be another.

But by imitation in art, Leonardo intended no slavish reproduction of
nature. When he wrote that "the painter strives and competes with
nature," he was on the track of a more Aristotelian idea. This he
barely developed, using nature only partly in the Stagirite's sense, of
inner force outwardly exemplified. The idea of imitation, in fad, as
it presented itself to his mind, was two-fold. It was not merely the
external reproduction of the image, which was easy enough to secure.
The real difficulty of the artist lay in reflecting inner character and
personality. It was Leonardo's firm conviction that each thought had
some outward expression by which the trained observer was able to
recognize it. Every man, he wrote, has as many movements of the body
as of varieties of ideas. Thought, moreover, expressed itself
outwardly in proportion to its power over the individual and his time
of life. By thus employing bodily gesture to represent feeling and
idea, the painter could affect the spectator whom he {xv} placed in the
presence of visible emotion. He maintained that art was of slight use
unless able to show what its subject had in mind. Painting should aim,
therefore, to reproduce the inner mental state by the attitude assumed.
This wa