"[E]ngineering itself is not just the application of mathematical equations but a subtle balance of aesthetics, economics and science in which culture counts as much as calculation. Computer-assisted design can accelerate execution of ideas but can never replace the insight that comes from immersion in the traditions of building. It was the cultural resonance of towers and polygons, used by brilliant designers, that made the targets of September 11 such powerful icons, not simply their acres of usable space."