Pacific Percy, thought it wrong to fight/But roaring Bill who killed him, thought it right.

So goes a bit of verse on the subject of pacifism that used to be recited to a friend of mine by his father. I use it here because it neatly sums up what I have always thought was the essential problem with the pacifist argument: Someone is always going to fight. Given that, someone else has to do the fighting for the pacifist.

This comes to mind at the moment because of the flap between New Zealand and the United States -- allies in the great and good fight against Soviet imperialism, communism and that sort of thing. Recently, New Zealand refused to allow an American Navy ship, the Buchanan, to make a port call because the United States would not say whether the ship was carrying nuclear weapons. This was in keeping with the policy of both governments: The United States never says whether a ship is carrying nuclear weapons; and New Zealand's new Labor government, headed by prime minister David Lange, refuses to allow nuclear weapons into the country. Fine. New Zealand is a sovereign nation and has the right to make its own policy regarding nuclear weapons. But it is also a signatory to the ANZUS pact, one of those Cold War-era alliances in which the United States, like a spider, wove a web and then, armed to the teeth with nuclear weapons, sat in the center and waited. The most famous of these alliances and by far the most important is NATO.

And probably the least important is ANZUS. Neither "A" (Australia) nor "NZ" (New Zealand) faces even the remotest Soviet threat. Still, the Reagan administration has reacted to New Zealand's new policy as if something very important is at stake. It has canceled naval exercises and has dropped some hints that it might look the other way when Congress tries, as it sometimes does, to end special trade preferences for New Zealand products such as cheese and lamb.

Probably both governments are overreacting. The administration is loath to see New Zealand set a precedent -- one that could be followed by allies that really count, the ones in NATO and, of course, Japan. In fact, conservative theorists have been long obsessed with Finland -- an independent nation Moscow intimidates by both proximity and history. From Finland, the eyes of conservatives dart nervously to even smaller Holland, yet another country some fear is slipping into a kind of neutrality. Commentary Magazine, alert to every sign of decadence in the West, has even detected a creeping neutrality in Dutch films.

This may be epic sillyness, but it is no less silly than the position of New Zealand's Lange government. If the ANZUS pact was worth signing and if it is worth keeping (a different issue entirely), then it's because New Zealand perceives some sort of threat either to itself or to world peace from the Soviet Union. If that is the case, and if America's nuclear shield has in fact contained Soviet imperialism, then nuclear weapons of the type New Zealand now scorns are what has done the trick.

The point is that New Zealand cannot have its cake and eat it, too. It cannot remain a member of an alliance designed to ensure its independence and, at the same time, insist on a policy that weakens that alliance. In doing so, it has adopted a version of the classic pacifist position -- not that of, say, Gandhi in India or even conscientious objectors during the Vietnam war, but of World War II pacifists in the United States. What made their pacifism possible was the willingness of others to do the fighting.

Certainly, New Zealand is so far from the world's usual tug-of-war zones that it can afford almost any kind of foreign policy it wants. Even in the event of atomic war, it may be outside the radiation zones and, absent atomic weapons, the retaliation zone as well. It is no great power with no commensurate responsibilities and it faces no threat of its own. But it ought to understand that in unilaterally telling the United States to shove off, it is not, as it thinks, announcing its independence but rather the triumph of interdependence. If it's secure enough to go it alone, the reason is that it's not really alone.