What Bernard Brodie said about nuclear weapons in 1946 continues to be true: The most important thing about nuclear weapons is that they exist and are terribly powerful. This was true in both the Cold War and the subsequent era. Although the situation has changed a great deal, there are striking continuities, especially in American attitudes and policies. Most obviously, the United States has consistently opposed nuclear proliferation, with only a very few exceptions for its closest friends. Second, the debate within the United States about the role of nuclear weapons has been altered only slightly by the end of the Cold War. The fundamental division between those who see nuclear weapons as having a revolutionary impact on world politics and those who do not continues. Trump’s Nuclear Posture Review makes arguments that are remarkably similar to those made under the Raegan administration. In parallel, the arguments made against Anti-Ballistic Missile (ABM) systems today are quite similar to those advanced during the Cold War, despite the radically changed conditions. This indicates that ways of thinking about nuclear weapons have become deeply engrained.