WHEN the decorator, having mastered the grammar of his art and studied the architectural requirements of the room to be furnished and the needs and tastes of its occupants, sets out to make the room beautiful, he is immediately confronted by the puzzling question: What is beauty? Fitness and comfort he can ensure by the due exercise of care and common sense. But how ensure beauty, an intangible and elusive quality which he can neither define nor even recognize with assurance? How go about it to give what is at best but a vague ideal concrete expression? How make a start in the actual processes of selection and arrangement? And, seeing that what one calls beautiful another calls un-beautiful, and that indeed there seem to be no fixed standards or norms of beauty, how shall he know, when his room is finished, whether it is beautiful or not?

These considerations do not trouble the great artist, who does what he has to do, as Lord Bacon noted, "by a kind of felicity." Nor do they trouble the great number of house-furnishers who do it in the same way, minus the felicity. But to those of us who are neither great artists nor indifferent to beauty, and who must see the ground beneath our feet before we take a step, they are questions of the most serious importance.

If we turn to books for answers to these questions we find that writers on interior decoration have for the most part ignored them, contenting themselves either with description and illustration, or with generalities too loose to be markedly helpful in practice; while from the writers on esthetics we learn that although philosophers from Pythagoras to Croce have sought to define it, beauty is after all a quality too subtle for definition. Like electricity, or like the life-force itself, we can experience it but we cannot tell what it is.

At first thought this looks like an impasse. However, the case is not as bad as it looks; for while it is true that beauty is beyond definition, and that no formulas exist for its creation, it is also true that the elements of beauty, or rather the conditions under which it appears, are fairly constant. If, therefore, we can cause these conditions to be present in our rooms we can be sure that beauty, in some degree at least, will be present also. The first of these elements or conditions, the one most easily apprehensible and most nearly susceptible in practice of reduction to general statement, and the one that constitutes the essential principle of beauty in the art of interior decoration, is the imaginative or sensuous expression of unity in variety.

Simply expressed, this means that before beauty can appear in it any work of art, whether it be a picture, a chair, or a furnished room, must consist of many parts; which parts, however numerous or diverse, must be so combined that they appear to concur in forming one whole. That is, they must present themselves to the mind as a unit, with a single aim, design and purpose. No bare room, no room which lacks a diversity of lines, shapes, colors and textures, of lights and shadows, of plain and ornamented surfaces, can be beautiful. Nor can any room be beautiful which, possessing this diversity, fails to fuse it into an essential unity. Conversely, no room so decorated that it reveals a stimulating degree of diversity, while at the same time its unity is perceptible instantly and without effort, can be wholly lacking in beauty.

It is therefore clear that the decorator will do well to disregard, at the outset, the more intangible and spiritual elements of beauty, which demand for their creation both imaginative power and a high degree of technical skill. These more subtle elements will come later, with the growth of creative power. At the outset it will be enough for him to arrive at principles of selection and arrangement through which the diversity of forms and colors necessarily appearing in the walls, floor and ceiling of his room, in its furniture and upholstery fabrics, its hangings, lamps, shades and pictures, can be coordinated and fused into the unity without which the room and its furnishings will be merely a congeries of unrelated parts, and as such unbeautiful. It is manifest that unity or the lack of it can be perceived only by the mind. To the nature of the mind, therefore, we must look for the solution of the problem.

The human mind is so constituted that it can grasp but a limited number of impressions at one time. Before it can comprehend a great variety of phenomena it must divide these phenomena into classes or groups, according to some principle of order. This principle is the arrangement of like with like. Thus primitive man, surveying the multitude of living creatures about him, observes that some fly in the air, and these he calls birds; while others, which live in the water, crawl upon the earth, or walk upright upon four feet, he calls fish, reptiles and animals. Observing further that some of the animals eat flesh, he marks off the carnivores, which are in turn divided into genera - as the canines and felines - and finally separated into individual species. Of course his groupings will not satisfy a later science. He will call the whale a fish, and the bat a bird. But the point is that they will satisfy his mind. When things look alike, or behave in the same manner - that is, when they have the same dominant qualities - he groups them together and is satisfied. Out of this process of grouping like with like have grown all the cosmologies, religions, sciences and arts, which, however widely they may differ in content, have for their common purpose the arrangement of like with like, and the organization of the phenomena with which they are concerned, whether they be gods or butterflies, in an order of dominance and subordination.

Since the mind works this way in all things, it will work this way in its apprehension of beauty; and without venturing into the field of physiological psychology we may assume the fact that whenever the mind is able without difficulty to recognize easily perceptible likenesses among a relatively wide range of objects and effects seen at the same time esthetic pleasure will result. That is, the mind will in some degree, however slight, feel the thrill of beauty. If it cannot recognize such likenesses, or can recognize them only with difficulty, or if the objects and effects perceived lack diversity, esthetic pleasure will not result. Thus the mind could see no beauty, but only confusion, in a hundred straight lines and right angles drawn at random on a sheet of paper, because of the total absence of likenesses among such stimuli. Nor could it see beauty in four of these lines arranged to form a square, and six more of them arranged to form a swastika, because of the lack of variety in the effects thus presented to it. But if the entire hundred were arranged in a design of squares and swastikas and border lines to form a Greek fret, the mind, easily perceiving the resemblances in the complex whole, would call it beautiful. The fret, to be sure, would not appear to possess a high degree of beauty because of its relative lack of diversity; but it would reveal some beauty because it would constitute an imaginative expression of variety in unity, one in the manifold.