Terrorism is the root of the destruction of the towers, as well as the hijackings of the four planes that crashed - two into the towers, one into the Pentagon, and one that crashed in Pennsylvania before it could crash into the Capitol or White House. Blaming anyone or anything other than the fanatical devotion to a corrupted worldview is to deny the fact that these individuals, and their leadership - Usama Bin Laden, seek to destroy the things that freedom loving people around the world hold dear.
Peace with security is what we must achieve. We cannot allow ourselves to be any less vigilant, especially in light of the anthrax attacks that are being perpetrated. Although we may not have conclusive proof that these attacks were caused by the al Qaeda group at the present, indications all point to that direction. It may only be a matter of time before those links are established.
Terrorism comes in many forms. It used to be that you would have to worry about a car bomb, a suicide bomber in a crowded square, or pipe bombs left in public spaces. Now, the world has to worry about whether its public health system can handle anthrax, other biological weapons, or chemical weapons or planes being crashed into highly visible symbols. A few people are even concerned about the use of nuclear weapons. These worries, and the ensuing conversations, would not have occurred before September 11, except in a novel or movie. Now, the movie pales in comparison with the reality.