George Keyworth was Science Adviser to President Reagan from 1981-1985. He begins the interview with a discussion of the Soviet focus on rocketry and a description of his notion that there have been two essential chapters in the nuclear age: a period of counter-value deterrence followed by a counter-force age involving targeting silos instead of cities. The latter, he says, has led to the concept of a window of vulnerability based on the prospect of one side seeing an advantage to launching first. Dr. Keyworth briefly describes the Reagan administrations early thinking about restoring a commitment to national security and particularly to nuclear stability, then compares it with Jimmy Carters conceptions. He says the current administration is not resistant to arms control, but sees it as just one of several tools for maintaining security. He denies that survivability has ever been a goal for Reagan, and that the point has always been prevention. The rest of the interview focuses in depth on the Strategic Defense Initiative (SDI) its origins and objectives, initial reactions to it inside the government, criticisms, and various technical aspects of the program. He believes the Reagan period will be seen as one of reversing the erosion of stability, and he has no doubt that SDI will survive if a Democrat enters the White House.