If we cannot agree on what is true and where to find the truth—even on whether there’s such a thing as truth—how can we develop, build support for, and carry out policies that defend our nation and deter our enemies?

As the number of missile-wielding states grows and as the nuclear club expands, the likelihood of a missile being unleashed against the American people or their allies—whether by mistake, miscalculation, or a madman—also grows. Missile defense doesn’t eliminate the danger, but it does give us a fighting chance to confront it.