To live in a border city is to live in a world divided, two worlds intimately involved with one another, inseparable, and yet in apparent contradiction. One cannot understand San Diego or Tijuana without comprehending what lies on the other side of the border fence. These cities are markedly different, but also interdependent. They are engaged not just geographically, but economically, socially, culturally, artistically, intellectually. They need each other in order to thrive. They need each other in order to subsist.