Robert Wright

About the author: Robert Wright, a visiting scholar at the University of Pennsylvania, is the author of The Moral Animal and Nonzero: The Logic of Human Destiny.

Pursuing a missile defense system would likely provoke other countries into expanding their nuclear arsenals, which in turn may make it easier for terrorist groups to obtain nuclear weaponsgrade materials. Thus, missile defense may actually increase the chances of another terrorist attack even more lethal than the one on September 11, 2001.

Some critics of President George W. Bush's missile-defense plan have already claimed a measure of vindication in Tuesday's [September 11, 2001] attack on the United States. Their logic is plausible as far as it goes: They've long been saying that massive destruction, when it comes, won't come via ballistic missile, and sure enough it didn't...