Three attributes of architecture have been recognized throughout the centuries - named variously "durability, convenience, and beauty" [46], or "commodity, firmness, and delight" [47]. In modern times it is tempting to consign these to distinct sub-disciplines - engineering, construction, and art - but architecture still seeks to define itself as a fusion of the three. In fact, however, the schism between designers and builders began to emerge as early as the fifteenth century, in the erection of Brunelleschi's dome over Santa Maria del Fiore in Florence [48]. Construction is now the business of contractors. Architecture is left to wrestle with the integration of engineering and art - disparate demands on the form and function of the built environment.
Until the mid-nineteenth century, engineering and art enjoyed a peaceful coexistence in traditional architectural materials, styles, and techniques that had evolved over centuries. With the dawn of the machine age, however, engineering began to emerge as a distinct discipline, armed with empirical data and mathematical methods that could prove a design's efficiency but not its aesthetic value. At the same time, building design became more complex, involving not only structural systems, but electrical and mechanical systems as well. Architects admired the functional purity of engineering design in the bridges, towers, and machines that heralded the new age. They rejected the outmoded formal trappings of bygone eras, and began to search for a new identity appropriate to modern materials, techniques, and demands. At the same time, they continued to profess the importance of art in design, and tended to view engineers - in Banham's words - as "noble savages".
Louis Sullivan's dictum - "form follows function" - has been the subject of much debate in architectural theory. In the extreme, it has been taken as a reductionist recipe for building design that concedes the entire process to engineering algorithms and renders architecture obsolete. On the other hand, Banham dismisses it as an "empty jingle". The Futurist architect Antonio Sant'Elia declared [49]:
That the new architecture is the architecture of cold calculation, temerarious boldness and simplicity ... That real architecture is not, for all that, an arid combination of practicality and utility, but remains art, that is, synthesis and expression.
Le Corbusier called the house "a machine for living in", but elsewhere argued [50]:
Architecture goes beyond utilitarian needs. You employ stone, wood and concrete, and with these materials you build houses and palaces. That is construction. Ingenuity is at work. But suddenly you touch my heart, you do me good, I am happy and I say "This is beautiful." That is Architecture. Art enters in.
Similarly, Mies declared [51]:
Our utilitarian buildings can become worthy of the name of architecture only if they truly interpret their time by their perfect functional expression.
Faced with the indisputable rationality of engineering calculations, architects have been hard pressed to develop a compatible system of aesthetics. They seek enduring formal principles that transcend passing fashion and applied decoration. The "functional expression" called for by Mies is ill-defined. Architects have often missed the mark, drifting from naked functionalism at one extreme to irrelevant formalism at the other. As of 1991, only about 20 percent of the total built output in developed societies has submitted to their professional pretensions [52, 53].
The investigation of Gestalt psychology and perception is one strategy for establishing a rational basis for aesthetics on a par with engineering. Nevertheless, architecture - like human consciousness - is not reducible to rational deduction. People respond to their environments emotionally as well as physically, and this must be accounted for in architectural function. As Prak explains: "If 'function' is so defined as to cover both the rational and emotional requirements of a certain purpose, then all architecture is 'functional'. The rational demand made of a town hall is that it serves as an efficient office building for the administration of the city; the aesthetic demand may be that it shows the dignity of the municipality" [54]. Aesthetic expression may evolve with culture over time, and may never be algorithmic, but it would be naive to pretend that it doesn't exist.