AT a time when international tensions and budget deficits are both increasing rapidly, many Americans are raising a perennial question: How much military spending can the United States afford? The truth is that the country can afford to devote a substantially larger share of its resources to military purposes than it now does. That simple conclusion, however, is only the beginning of serious analysis of the subject. A host of related questions quickly come to mind: What is the real cost of maintaining a large military establishment? Are there limits to the size of the military budget? How much military expenditure is enough? Does military spending stimulate or retard economic growth? What is the exact relation between spending on guns and on butter? Economic analysis can cast considerable light on these important issues and help us to formulate budget priorities. In the end, though, it is mainly political criteria that must determine how much of our resources we allocate to national defense, and a political question as to how much we are willing to spend.