Many students in their early essays draw rather from an imagined knowledge than from the actual visual aspect--are apt to take forms for granted, to assume, for example, that an object is round when it is really subtilely polygonal. Theoretically a curve has no existence, being really a combination of straight lines varying in length and direction. Many beginners are unable to approximate even so obvious a form as a right angle, and until their vision and judgment is trained, it is improbable that they can successfully render more subtile combinations. It is the business of the teacher to train the vision so that the perceptive faculties are developed, and instil in the mind of the student that art is only concerned with appearance. Any fact not visually apparent should be ignored.
The whole subject is complicated by convention; thus for convenience, forms are drawn in outline, but these drawings are not representations, and are only recognisable and accepted as such through education and tradition. Drawing in outline is merely to sequestrate a portion of the surface by a line or lines, and can only define at most two dimensions. When shade and shadow are added there is some approximation to the solid in the suggestion of the third dimension. Though these tend to a more lucid explanation, the work remains a convention if colour and atmosphere are rendered in monochrome.
It is generally assumed that appreciation for colour is inherent. That this to some extent is true is evident in the attraction of bright colour to the child and the savage. Subtle quantities and combinations are only appreciated by comparatively few, the faculty for colour being extremely rare.
The average individual is guided as a rule in colour selection by vogue or fashion, though it is the polite custom to concede that the average woman is naturally endowed with taste. This is delicate ground, but the awful and impossible associations evident at times in feminine costume certainly do not justify the courtesy. There are superstitions in colour selection evidently the result of tradition, such, for instance, as red and yellow being suitable for a sallow complexion. The actual effect of these colours being to excite the complementaries, is hardly favourable to the misguided wearer.