Ten years later and it's still impossible to make sense of it. I cannot understand how a group of people formed a conspiracy and then carried out a plan to murder thousands of people they'd never met. Whatever your political beliefs, no agenda or religious idea can justify mass murder. And ultimately, that's all it was. Murder.
The attacks killed many people. Injured and sickened others. Terrorized millions. Created widows and orphans. But what did the attacks accomplish? They helped start the wars in Afghanistan and Iraq, plus the global war on terrorism. They disrupted the world economy and caused a great deal of property damage. But really the only change the attacks brought was to add more suffering to the Earth. To visit war and death and destruction on yet more people.
This emptiness. This lust for destruction. This mass murder of others is evil. Simple evil. There is no explanation sufficient, no justification, no rationalizing. You can't explain it. You can only look on it in horror.