How well an expert naturalist, who can also draw, imitates objects by recognizing and emphasizing the important and significant parts from which is derived the character of the whole! Just as the artist is greatly helped by an exact knowledge of the separate parts of the human figure, which he must in the end regard again as a whole, so a general view, a side glance at related objects, is highly advantageous, provided the artist is capable of rising to Ideas and of grasping the close relationship of things apparently remote.

Comparative anatomy has prepared a general conception of organic creatures; it leads us from form to form, and by observing organisms closely or distantly related, we rise above them all to see their characteristics in an ideal picture.

If we keep this picture in mind, we find that in observing objects our attention takes a definite direction, that scattered facts can be learned and retained more easily by comparison, that in the practice of art we can finally vie with Nature only when we have learned from her, at least to some extent, her method of procedure in the creation of her works.
Furthermore, we would encourage the artist to gain knowledge also of the inorganic world; this can be done all the more easily since now we can conveniently and quickly acquire knowledge of the mineral kingdom.
The painter needs some knowledge of stones in order to imitate their characteristics; the sculptor and architect, in order to utilize them; the cutter of precious stones cannot be without a knowledge of their nature; the connoisseur and amateur, too, will strive for such information.
Now that we have advised the artist to gain a conception of the general operations of Nature, in order to become acquainted with those which particularly interest him, partly to develop himself in more directions, partly to understand better that which concerns him; we shall add a few further remarks on this significant point.
Up to the present the painter has been able merely to wonder at the physicist's theory of colors, without gaining any advantage from it.
The natural feeling of the artist, however, constant training, and a practical necessity led him into a way of his own.

He felt the vivid contrasts out of the union of which harmony of color arises, he designated certain characteristics through approximate sensations, he had warm and cold colors, colors which express proximity, others which express distance, and what not; and thus in his own way he brought these phenomena closer to the most general laws of Nature.

Perhaps the supposition is confirmed that the operations of Nature in colors, as well as magnetic, electric, and other operations, depend upon a mutual relation, a polarity, or whatever else we might call the twofold or manifold aspects of a distinct unity.
We shall make it our duty to present this matter in detail and in a form comprehensible to the artist; and we can be the more hopeful of doing something welcome to him, since we shall be concerned only with explaining and tracing to fundamental principles things which he has hitherto done by instinct.
So much for what we hope to impart in regard to Nature; now for what is most necessary in regard to Art.
Since the arrangement of this work proposes the presentation of single treatises, some of these only in part, and since it is not our desire to dissect a whole, but rather to build up a whole from many parts, it will be necessary to present, as soon as possible and in a general summary, those thing's which the reader will gradually find unfolded in our detailed elaborations.