New York was very tense this morning. The person who'd placed the pressure cooker bombs in Chelsea last night was at large. Many of us were woken up by a text message with the name of the suspect; he was later apprehended in New Jersey. The unease involved both worry about what had happened and worry about the sort of over-reactions it sought to provoke (and, of course, did) - New York has experienced this lethal cascade before. For now, if the man arrested is indeed the perpetrator and acted alone, peace is restored. The unease remains.