During the Renaissance, the five senses were understood to form a hierarchical system from the highest sense of vision down to touch. Vision was correlated to fire and light, hearing to air, smell to vapour, taste to water, and touch to earth.
Perhaps the human fascination with fire stems from the totality of its sensory stimulation. The fire gives a flickering and glowing light, ever moving, ever changing. It crackles and hisses and fills the room with the smells of smoke and wood and perhaps even food. It penetrates us with its warmth. Every sense is stimulated and all of their associated modes of perception, such as memory and an awareness of time, are also brought into play, focused on the one experience of the fire. Together they create such an intense feeling of reality, of the "here and nowness" of the moment, that the fire becomes completely captivating.
Districts have to help bring the resources of a city down to where they are needed by street neighborhoods, and they have to help translate the experiences of real life, in street neighborhoods, into policies and purposes of their city as a whole. And they have to help maintain an area that is usable, in a civilized way, not only for its own residents but for other users—workers, customers, visitors—from the city as a whole.
To accomplish these functions, an effective district has to be large enough to count as a force in the life of the city as a whole. The “ideal” neighborhood of planning theory is useless for such a role. A district has to be big and powerful enough to fight city hall. Nothing less is to any purpose.