Professor Koch thus defines the difference between the easel-picture painter and the painter of mural decorations: "I call the painter 'decorative' who adorns the architecture on the surfaces of wall or ceiling with painting. I understand by the term 'Lower Art' or 'easel painter' the artist who puts upon canvas with colour and brush what his eye or his fancy pleases, sends his work in a gold frame to the picture exhibition, where it is then bought by some purchaser and can be put in a place for which it was not planned. The decorative painter is often assigned a definite place to fill and has to make the whole composition painter-like." The easel-picture painter is trained to the imitation of nature, often as an end instead of a means to an end, and in a portable object of this kind the aesthetic mistake is not very visible, but transfer the technique or strive to realise the same aim upon the wall and the failure from the point of view of Abstract Art becomes painfully evident. It is forgotten that as Professor Baldwin Brown says: "mere imitation of nature is not in itself artistic though it brings into existence the raw material of art. The imitation is only made artistic by the operation of the controlling law of composition." This is not a mistake made only in modern times, the craftsman has always rejoiced in getting as near to nature as possible, and "from the very beginning of art history, so soon at least as the carver or painter had attained some success in the imitation of nature, the popular eye has looked at his work almost entirely as representing nature," a matter of little importance when detached and movable objects only are in question, but when permanent decorations which cannot be removed from their places are produced it becomes of great importance that true principles should govern their design and execution. One must repeat that the painter whose principal ambition it is to realise the appearance of nature, giving her subtle aerial perspective by the accurate rendering of delicate gradations of tone as the various objects sink farther and farther into the sea of light and atmosphere which bathes every natural scene, and in a less perceptible degree the personages composing nearer groups—in so far as he attains his aim produces that which is unfit for mural decoration—since his success means the appearance of an opening in the wall through which the scene he has represented may be viewed by the spectator; whereas the object of mural decoration is obviously the decoration of the wall-surface, not its removal The frescoes of Mantegna in the Eremitani church at Padua show the only possible way of employing a mode of painting with considerable use of realism without much offending one's aesthetic sense. Here the pictures are framed within architectural forms, so that if the pictures were indeed spaces through which the scenes depicted were viewed, the roof would still be supported by the architectural skeleton of column and entablature which serves as frame.

The habit of mind engendered by constant striving after success in realising the effect of natural objects, is not only unhelpful to the painter whose business it is to decorate a wall-surface, but actually harmful, since it diverts his mind from the consideration of those problems which it is imperative that he should meet and solve. It can scarcely be too strongly insisted on, that while nature must necessarily form the basis of the painting, and the most earnest study of form and colour must precede the attempt to produce any work of decoration which is to be impressive, the imitation of nature is only useful in so far as it renders the meaning of the painter clear; and for the mural painter the question of a treatment in harmony with the surroundings of his picture, and of such a nature as to make his painting visible, either at a considerable distance or at some strange angle, or in semi-obscurity as may often chance, is of infinitely more importance than the accurate representation of nature. And with this question of treatment is bound up the total effect of the conception of the general scheme, for it is quite easy for the painter to dwarf the proportions of a building, or to exaggerate any defects which it may have, by adding paintings which are out of scale in one way or another, or unsuitable to the style of design chosen: and he, in common with the other craftsmen whose work should combine to form an impressive and agreeable whole, must recognise the necessity of sacrifice, at the risk of producing a monstrosity, by the contest of each portion for supremacy.

Sir W. B. Richmond once said that" in decoration it was no use to copy nature: they must have learnt nature and have nature at their fingers' ends, and they must learn that lesson which came to them late in life, i.e. what to leave out." One is inclined to go even further, and say that the representation of nature is only important in as far as it assists the conception of the designer's meaning and produces beautiful line, form, or colour; and the more abstract the mode of representation chosen is, that is to say the fewer the means of expression which are retained, the more absolute must be the perfection with which the expression is made in those few. For instance, if figures are painted on a wall in full light and shade and colour, faults in drawing may be pardoned if the colour is good, and the intelligibility of the whole is not much lessened by their presence though its beauty may be; but if the same figures are to be expressed in outline filled in with flat tints, the silhouette and drawing of the limbs must be better than before if an equal aesthetic impression is to be produced, and a greater care must be bestowed upon the arrangement of every line of the composition, since everything is displayed, whereas in the former case some portions would be salient and others more or less lost. " Beauty in works of art is of at least as much importance as truth," says Professor Baldwin Brown, "unless nature be made obedient to the aesthetic purpose, unless beauty result from the imitation of nature, such imitation is vain "— a sentence which one could wish dinned into the ears of artists, craftsmen and patrons, till it became part of their very being; in which case much fruitless labour would be saved, much waste of good money would be prevented, and the comparatively few who are not led by fashion in their admiration of art objects, would not have their feelings harrowed by the sights which now too often make them sigh. We want greater co-operation and sympathy between painters, sculptors, craftsmen, and architects. What Latilla wrote in 1842 is still much too true. " In modern times, sculptors and architects in general have little regard for what is pictorial, and painters are not at all interested in what is architectural; and while the Italian rose in the united strength of the three, the artist of this day thinks nothing is to be derived from any branch but the one he owns".