Experts tell us the meaning of what they haven’t seen; poets and novelists tell us the meaning of what they haven’t seen, either, but have somehow managed to fully imagine. Maybe the literature of terrorism, from Conrad to Updike (and let us not forget Tolstoy, fascinated by the Chechens), can now throw a little light on how apparently likable kids become cold-hearted killers. Acts of imagination are different from acts of projection: one kind terrifies; the other clarifies.