The fewer links there are in the visual information the observer receives, the greater the effort he has to make. The architect, then, introduces structures which make it possible to group the elements by strengthening their relationships. Most towns and architectural works are characterized by several superimposed levels of organization in a hierarchy specific to the composition. The level of interest of a work does not lie so much in the use of one or other of these methods or organization, but the knowledge of these methods increases our consciousness of the design resources available and our skill in handling them.
The eye perceives texture when the parts of a surface are sufficiently close, similar and numerous that they are no longer seen individually as figures. By analogy we can talk about a homogeneous structure when the same principle is applied to objects or buildings in space (for example a forest, a medina in North Africa, etc.). The most elementary structure is thus created simply by proximity, repetition, similarity and, sometimes, by the orientation of the elements.
Certain textures are in danger of disintegrating because they contain too many breaks and irregularities (Figure 46). The introduction of roads and buildings on the random alignment of previous agricultural subdivisions is often the root cause of the confusion of our modern suburbs. No sooner is a rule established than it is broken. The fabric does not get its chance to be woven. We have based our argument on aerial views because they are comparable documents. We could just as well have observed the texture of façades or of fragments of façades.
In a repetitive structure like texture or series, the intervals or elements may gradually change their form, size or orientation. Gradation thus combines two contradictory characteristics: relationship and difference without a pronounced hierarchy . Gradation is found everywhere in our environment. Many of the elements of nature are structured in this way . Without attaching too much importance to an analogy between the human body and the façade of the Convent of La Tourette. Frequently found in nature, gradation is, however, little used in architecture. More regular rhythms are generally preferred, for obvious reasons of economy of building methods.
There exists one particular form of gradation which is used more often in plan and section than in façades: progression. It is a continuous gradation of crescendo without cyclical variation. Thus a hierarchy is established as can clearly be seen in the drawings of the southern temple at Thebes by Auguste Choisy where the progression towards the heart of the sanctury can be read not only in the plan but also in section. It is not the highest and the largest which is the most important, but the opposite. Hierarchy is not a question of size but of the relative position of an element in its context.
A hierarchy implies primary and secondary elements. There is a dependent relationship between these elements; one or several of them dominate the others. Within these elements the same phenomenon can take place: by concentrating attention on one element, this one can become primary and we then discover secondary elements. In diversity, hierarchy is a powerful unifying factor. It makes it possible to combine elements in bigger, simpler and more recognizable entities.
Whoever talks about ‘hierarchy’ in the built environment thinks only too readily of ‘axis’, ‘symmetry’, ‘centrality’, etc. It would be pointless to enumerate all the means which can contribute to the dominance of an element in its context. In any case, symmetry is not the only means of achieving it. Even the simple changing of the orientation of a building in relation to others is sufficient, by being an exception, to establish an unabiguous hierarchy.
Hierarchy thus implies a dominance of spaces or objects. We use hierarchies every day in the organization of our thoughts. We need these references to facilitate our orientation in complex space. When there are too many hierarchies of equal value, the clarity of the hierarchy breaks down.
- 曲 /直（柯布西耶）。
Contrast serves to give an immediate and unambiguous identity to two formal systems. It leads to mutual reinforcement without necessarily resorting to explicit hierarchy. The interdependence of the elements is achieved by tension resulting from their opposing characteristics.
Contrast enables us to establish differences: we have seen it with the figure/ground phenomenon. Moreover, two opposites placed in a contrasting situation establish a ‘dialogue’ between them. With three, four or more, that becomes difficult, or even impossible. Contrast is a principle for ordering our environment. The meaning of a form is accentuated by its opposite.
The concept of complexity in architecture can be defined by its opposition to simplicity, indeed to what is clear and elementary. Looking at the Parthenon from an oblique angle, we can guess at the sides hidden from view. All its elements, base, columns, capitals, architraves, etc., blend to create a unity, preventing all ambiguity of interpretation. Whilst being infinitely refined, this temple remains, at the same time, of utmost simplicity. The eye is invited to accept it more than to explore it. It is quite a different matter with Michelangelo’s façade of San Lorenzo. In spite of the symmetry, which is a powerful unifying factor, we find ourselves in the presence of several co-ordinated and superimposed similar formal structures. The elements are grouped in such a way as to present more than one interpretation to the observer – that is what we call complexity. Supposing the façade were built and we gradually approached it – although the same holds true from a fixed viewpoint – the façade alternates among several formal organizations which dominate in turn. It becomes a façade to explore . Colin Rowe and Robert Slutzky have introduced the concept of transparency from which they develop an interesting, critical tool for analysing and composing with these phenomena of superimposition.
We meet, however, many involuntary and clumsy complexities (and simplicities) in architecture. The exceptional quality of San Lorenzo lies in the control of the dependency between the elements and the geometries. The balance between them makes the façade complex without being complicated, in the same way that the Parthenon is simple without being banal. The mastery of complexity in architecture, as with simplicity, can only be the fruit of assiduous labour. It is not simply a question of talent, as Bernhard Hoesli51 shows very clearly when he lines up the preliminary sketches of Michelangelo. The first design is still ‘clumsy’: the geometric subsystems do not yet intersect to form a whole; they are juxtaposed. Other methods also exist for working with complexity, as for example, deviation from a norm. It can result from the introduction of divergences from an established symmetry, or even from an anomaly in a regular pattern, or simply from the distortion of a familiar figure.
Let us examine, as an example, Richard Meier’s High Museum in Atlanta. Where does the cohesion come from in this geometric complexity and multitude of volumes and spatial situations? Here the ‘controlled complexity’ is no longer restricted just to the façades. On the exterior, a great unity of materials comes from the cladding of square, metallic panels which form a homogeneous texture independent of the geometry and function of the individual volumes. This continuity of texture is essential to combine the irregularities into one unit identifiable by the layman. In the organization of the internal space, the de-formations are particularly numerous. The initial orthogonality is broken from one change of angle to another, so insistently that there is a risk of total disorder. Three features of the layout prevent such fragmentation:
- the changes of angle in the end create, at least partially, a new orthogonality between them;
- they almost always relate back to the exterior by transversals;
- the large central space, in the form of a quadrant, acts as a reference throughout the main stages of the architectural promenade.
The cohesion is precarious, intriguing and provocative. It is not certain that this is the best place for displaying works of art, but Meier insists on the ability of the architecture itself to be ‘art’. This balancing act between obvious order, hidden order and disorder is fragile. This is what fascinates the minds, when such a work reflects not only poetic inspiration, but also skill combined with knowledge of the means for achieving it, as these two examples, several centuries removed, demonstrate.
The purity of the Renaissance was then rejected in favour of an expressive and sarcastic freedom, allowing the caprice of functional discord by the modification of codified elements. We also find traces of Mannerism in the architecture of the nineteenth and early twentieth centuries, aimed at freeing architecture from academic rationalism. We can perhaps agree with Serlio who said, already in the sixteenth century, that novelty is pleasing in so far as it does not erase all the rules. In contemporary architecture it is Robert Venturi who has set his hand to a re-establishment of the notions of contradiction and ambiguity with a view to freeing himself from the sometimes dogmatic simplicity of modern architecture. He expresses himself through his schemes and his writings: ‘I am for richness of meaning rather than clarity of meaning’.53 He sets the hybrid against the ‘pure’, the compromising against the ‘clean’, the ambiguous against the ‘articulated’. Whether architecture is at the same time large and small, continuous and articulated, open and closed, structure and decoration, relates to the links between the parts and the whole. These double choices express a commitment to questioning the simplicity of modern architecture by using a deliberate selection of historical precedents.
In chaos, no factor of coherence at all is at work. If any subsist they cancel each other out, because no structure, no formal or semantic theme is any more dominant, neither in the individual parts, nor in the whole. There is a conflict or absence of rules. The number of conflicting elements is high. As Arnheim points out, disorder is not homogeneity, even if the latter is at a very simple level, but a disorder between partial orders. ‘An orderly arrangement is governed by an overall principle; a disorderly one is not.’
Certain neighbourhoods of our cities have gradually taken on a chaotic form in the course of this century. This disorder reflects their recent transformation into an accumulation of transportation systems, objects and buildings which take only their own utility into consideration, without any common objective of creating a city. Friedrich Schinkel was already warning in 1840: ‘No single need produces beauty, circumstantial utility cannot determine form without engendering chaos.
Could chaos itself become a source of creation and life? Nietzche said that chaos was needed for a star to be born. If that is really the case, we can expect to see a very beautiful star. Unless society has completely crumbled away, forgotten its past, been uprooted and lost all capacity for hope, its architects and its planners do not have the right to be the accomplices of chaos. Urban chaos is a state of instability. On one hand, it tends to become organized by signs of occupation. On the other, being accustomed to a city helps us to learn about its more secret order. The inhabitant of the homogeneous kasbah has an organized centre – his house – from were he constructs a complex network of relationships which make the apparent confusion intelligible.