Strategic defense and the global public good
To deserve serious consideration, a strategic defense system must pass four tests: (1) it must be technically feasible. (2) It must preserve the war avoidance stability of mutual deterrence. (3) It cannot be so expensive that an adversary can cheaply overwhelm it. (4) It must be politically feasible. Historically, proposed strategic defenses have failed all four tests. But recent changes could make strategic defense prospectively viable if provided as a global public good. Rather than defense to advance individual national interests, universal missile defense to limit damage globally may pass all four tests. Historically, Mutual Assured Survival has been postulated as a substitute for MAD deterrence. But a global defensive system would mean we can have both mutual survival and mutual deterrence.