Someone may claim that abstract art is trash, and then go home and cover their walls with it in the form of wallpaper. A company president might declare that art should be realistic, only to authorize the spending of a fortune for a purely abstract business logo. Colour, shape, and composition affect our visual aesthetic sense, and with it, our psychology and behavior. Many of these things go beyond cultural customs, and apply wholly to our human identity. In evaluating Celtic art, we must ignore personal preference and focus our attention on more elemental matters.
Human beings prefer harmony to discord.
Two shapes in proximity must contain harmonics of each other if the results are to be naturally felt as pleasing. Repetition leads the eye, and if the eye is thus led in patterns that are harmonics of design elements within the object viewed, then the aesthetic sense is aroused. When shapes are in proximity, other shapes are created out of the spaces in between. Care must be taken by the artist to insure that, even if the shapes are themselves in harmony with each other, the resulting spaces do not form shapes that are discordant, and clash with the positive elements. This consideration of positive and negative shapes is absent in the majority of artistic traditions, although in modern art it is sometimes employed.