Nature is separated from Art by an enormous chasm, which genius itself is unable to bridge without external assistance.
All that we perceive around us is merely raw material; if it happens rarely enough that an artist, through instinct and taste, through practice and experiment, reaches the point of attaining the beautiful exterior of things, of selecting the best from the good before him, and of producing at least an agreeable appearance, it is still more rare, particularly in modern times, for an artist to penetrate into the depths of things as well as into the depths of his own soul, in order to produce in his works not only something light and superficially effective, but, as a rival of Nature, to produce something spiritually organic, and to give his work of art a content and a form through which it appears both natural and beyond Nature.
Man is the highest, the characteristic subject of plastic art; to understand him, to extricate oneself from the labyrinth of his anatomy, a general knowledge of organic nature is imperative.

The artist should also acquaint himself theoretically with inorganic bodies and with the general operations of Nature, particularly if, as in the case of sound and color, they are adaptable to the purposes of art; but what a circuitous path he would be obliged to take if he wanted to seek laboriously in the schools of the anatomist, the naturalist, and the physicist, for that which serves his purposes! It is, indeed, a question whether he would find there what must be most important for him.

Those men have the entirely different needs of their own pupils to satisfy, so that they cannot be expected to think of the limited and special needs of the artist.

For that reason it is our intention to take a hand, and, even though we cannot see prospects of completing the necessary work ourselves, both to give a view of the whole and to begin the elaboration of details.
The human figure cannot be understood merely through observation of its surface; the interior must be laid bare, its parts must be separated, the connections perceived, the differences noted, action and reaction observed, the concealed, constant, and fundamental elements of the phenomena impressed on the mind, if one really wishes to contemplate and imitate what moves before our eyes in living waves as a beautiful, undivided whole.

A glance at the surface of a living being confuses the observer; we may cite here, as in other cases, the true proverb, "One sees only what one knows" For just as a short-sighted man sees more clearly an object from which he draws back than one to which he draws near, because his intellectual vision comes to his aid, so the perfection of observation really depends on knowledge.