In minor ways, world opinion can serve as some kind of brake on full-scale utilization of the technology of terror and destruction. There has, as yet, been no use of nuclear weapons in Vietnam; and although rural populations are considered fair game for any sort of military attack, urban areas, where the butchery would be more evident to the outside world, are still relatively immune. Similarly, the use of gas attacks and chemical warfare has been extended only slowly, as habituation permits each gradual increment to pass unnoticed. But ultimately, the only effective brake can be popular revulsion on a mass scale in the United States itself. Consequently, the level of culture that can be achieved in the United States is a life-and-death matter for large masses of suffering humanity. This too is a fact that must color any discussion of contemporary American institutions.