A GOVERNMENT that campaigns for human rights need to be precise about its purposes. Last weekend Secretary of State Cyrus Vance usefully began to lay out a series of clear principles for the Carter administration to follow. Ever since Woodrow Wilson, Americans have understood that these attempts to impose their morality on other nations are perilous. But most Americans consider it a national responsibility to keep trying, and some of the consequences are already beginning to nip at President Carter's ankles. Mr. Vance, in his speech at the University of Georgia, was sharpening the public definition of the administration's intentions.

Enthusiasm is not an adequate substitute for intellect. When an administration begins to chide other governments for inadequate attention to their citizens' rights, it lays itself open to charges of inconsistency. Why punish Argentina and not South Korea? The answer lies, of course, in an assessment of American national interests. Pressing some countries is risky, pressing others is not. It's best to be quite candid about that.

Mr. Vance is evidently beginning to worry about the exploitation of the human-rights issue in Congress. When the House passed the Harkin amendment last month, it demonstrated the kind of trouble that can spring up. The amendment would require the United States to oppose loans by the World Bank and other international agencies to countries engaging in "gross violations" of human rights. The vote was carried by a strange alliance between the super-pure and those earthly souls who simply don't like foreign aid and saw the rights campaign as a convenient device to cut it. There are a good many other opportunities of that sort lying around. Not many congressmen like to be called protectionists, for example - but some of those troublesome imports of shoes and steel and clothing come from countries that might be said to violate one definition or another of human rights.

If Mr. Carter's defense of rights abroad is to survive, it is going to have to be stated more exactly than he has yet attempted. He is going to have to deal explicitly with the Wilsonian dilemma. The United States can't run the whole world. But neither can it ignore its obvious power, in some places and in some circumstances, to improve the condition of people living under oppressive governments. Mr. Vance's speech in Georgia was more careful than some of Mr. Carter's observations on the same subject. We read the Secretary's words as the attempt of a good lawyer to refine and focus a presidential position. That position is a courageous and valuable one but, at the moment, it seems to mean something a bit different to each person who hears it.