Two airplanes destroyed the World Trade Center towers Tuesday morning, another crashed into the Pentagon, and other apparent terrorist attacks were reported around the country. (Get the latest from MSNBC.) Earlier this year, Robert Wright made the argument against missile defense as protection from terrorist attacks. Click here to read the story. In "The Book Club," Peter Ringle and Gideon Rose discuss three books on terrorism. Click here to read it. In this "Explainer," Bruce Gottlieb discusses why terrorists don't always take responsibility for their attacks. Last year, Emily Yoffe explained the backgrounds of Hamas, Hezbollah, and other terrorist groups.