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This Chapter argues that ornament is valuable for us to experience architectural form in a positive way. Chapter 3 presented mathematical reasons for why ornament is necessary. The visual coherence of a complex form, as defined by systems theory, requires ordered substructure on all scales: from the overall size of the building, down to the detailed grain in the materials. Natural structures have this (essentially fractal) property. If a man-made form lacks ordered structure on one or more obvious scales, it is perceived by human beings as being visually incoherent, and consequently as alien to our conception of the world (which is based on visual consistency). A building’s visible substructure on the range of scales from 1 mm to 1 m has been achieved in the past through traditional ornament and detail.

Our neurophysiology is set up so that we expect visual input from our surroundings to contain many of the characteristics of traditional ornament. Human visual and mental make-up is linked through evolutionary processes to the informational richness of our environment. This biological background helps to explain some aspects of why human beings create ornament. Going deeper than the usual “artistic” analysis of architectural ornament, I try to place it within the context of shared biological mechanisms. It is part of human nature to order our world and establish scaling relationships so as to better understand our relationship to it. Here, I will present several rules derived from our cognitive mechanism — these rules are intended to help understand how we conceive a form as visually coherent, and thus meaningful. I then discuss the relationship between cognitive rules and the creation of ornament.

Altogether, eight “cognitive rules for structural order” can be established. They represent the neurophysiological equivalent of the three laws of structural order presented in Chapter 1, together with detailed rules for achieving scaling coherence given in Chapters 2 and 3. It is remarkable that the concept of structural order can be reached from three entirely different viewpoints: we can use science to discover how structures are put together coherently; we can use art and architecture to do the same thing; and we discover that our own mind works in precisely the same way. This reveals a universality for all the concepts discussed in this book — a level of validity that cannot possibly be dismissed as accidental.

Table 4.1.	Summary of the Eight Cognitive Rules.
1.	A region of contrast, detail, or curvature is necessary.
2.	The center or the border should be well-defined.
3.	Attention is drawn to symmetric ornamental elements.
4.	Linear continuity orders visual information.
5.	Symmetries and patterns organize information.
6.	Relating many different scales creates coherence.
7.	We connect strongly to a coherent environment.
8.	Color is indispensable for our well-being.

I propose two arguments against both the minimalist design, and the random design of built forms. The first is that both cause anxiety and physiological distress, because they inhibit human mental connection with a given structure, normally experienced when meaningful information is available. Minimalist design omits aspects of warmth and comfort from our surroundings. A geometrically pure space can generate anxiety. The second argument centers on a concern about a very disturbing similarity. Minimalist and disordered built environments resemble the perception of a normal, visually complex environment by persons with a damaged perceptual apparatus or cognitive mechanism. I shall discuss how different types of injury to the eye and brain result in precisely the same effects offered by either minimalist or intentionally disordered design. This coincidence is serious because our body is programmed to respond to and so avoid perceptual and cognitive damage, and environments that are deliberately conceived in this manner are often triggering a reaction of distress.

The broader implication is that architecture adapted to human beings requires ornament for a sense of well-being. To prove this in a fully rigorous fashion is outside the scope of the present Chapter. I acknowledge other factors that influence the appreciation of architecture, including past experience, cultural formation and environment, and upbringing. Other authors argue for innate preferences for certain types of physical landscape, giving convincing reasons based on the environment’s fractal qualities, which support the necessity for ornament and detail. At the same time, however, it has been shown that innate preferences are displaced by factors such as familiarity and psychological conditioning. It is probably true that living life in a minimalist architectural environment will make a person more familiar with it, yet such types of structure are not in harmony with our neurophysiological make-up.