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. M. C. Escher is known for making clever use of the device. These are just a few aesthetic principles that transverse cultural differences and can be applied to Celtic art.
Celtic art is predominantly abstract, but that abstraction is a reflection of nature.
In our culture, when we go on a walk to view nature, we perceive collections of things, a macrocosmic impression of trees, hills and streams. The Celt was more likely to see a single leaf unfurling in a spiral, or a bud beginning to open. We may be aware of these things, as well, but if is a matter of emphasis, and the degree of influence on our art. When nature is viewed as a whole, some of the mystery is lost, for it is the awareness of the similarities of its parts, or the underlying laws that connect disparate objects of nature, that the aesthetic sense is rooted in. In this way the aesthetic experience is strongly connected to the religious experience, and with Celtic art it is often difficult to differentiate between the two, if indeed such differentiation is appropriate.