architecture satisfies a basic, universal human need for a roof over one's head. More than walls, more than a chair to sit on or a soft bed to lie on, a roof is the classic symbol of protection and security. We've all heard the expression “I have a roof over my head,” but it would be unusual to hear someone say, “I'm all right because I have walls around me.” Of course, in purely practical terms a roof does keep out the worst of the elements, snow and rain, and in warm climates a roof may be sufficient to keep people dry and comfortable. The roof seems to be symbolic of the nature of architecture.
More than any of the other arts, architecture demands structural stability. Every one of us daily moves in and out of buildings—houses, schools, offices, stores, churches, bus stations, banks, and movie theaters—and we take for granted, usually without thinking about it, that they will not collapse on top of us. That they do not is a tribute to their engineering; if a building is physically stable, it adheres faithfully to the principles of the particular structural system on which its architecture is based