also joining us is james traub and harvard professor matthew bunn who developed a secret study for president clinton on the study of nuclear materials in russia. professor bunn, first to you, in your reading of this deal, what is your ultimate assessment of it? >> i do think it's an important breakthrough that will reduce the spread of nuclear weapons around the world and, in particular, in iran. it's actually a bit better than i would have expected would have been possible, given the hostility and the stiff neck of the iranian regime. you have provisions designed to cut off or at least hem in each pathway iran may take on the bomb. on the uranium enrichment, they are cutting back two-thirds of their centrifuges and the stock