By a one-vote margin, the Supreme Court yesterday nullified a controversial ruling that a New Hampshire state college had illegally discriminated against a woman faculty member because of her sex.

Christine M. Sweeney of Keene State College, a liberal arts division of the University of New Hampshire, was hired as an associate professor of education, starting with the 1969 spring semester. Twice she requested promotion to full professor and unanimous all-made panels turned her down both times; she finally succeeded in 1976.

In a lawsuit, Sweeney accused the college of violating the prohibition against sex discrimination in the Civil Rights Act of 1964.

The suit blamed sexual bias not only for the denials of promotion, but also for lower salaries generally paid to women faculty members whose workloads at Keene are substantially equal to those of their male counter-parts.

In April 1977, U.S. District Judge Hugh H. Bownes ruled for Sweeney. He said that she was a victim of sexual discrimination the second time she sought promotion, and that there was a discriminatory pattern in "hiring promotion, and salary."

Bownes ordered a promotion and back pay for Sweeney, both retroactive to 1975. Last January, the 1st U.S. Circuit Court of Appeals upheld him.

One issue was the reluctance of federal courts to involve themselves in campus hiring, salary and promotions decisions. The 1st Circuit said "judicial deference" shouldn't be carried so far as to result "in judicial abdication of a responsibility entrusted to the courts by Congress."

In a petition for review, however, the college said that the lower tribunals had disregarded the Supreme Court's caution about "judicial intrusion into academic and administrative decision-making."

By contrast, Sweeney's lawyers said that the college's position, carried to its "logical conclusion," would be continuation of "the same sort of egregious discriminatory practices on campuses across the land . . ."

The American Council on Education, composed of nearly 1,300 nonprofit higher educational institutions and 169 educational associations and organizations, sided with Keene State.

The lower courts' decisions "gravely threatened" the "independence and integrity of the academic enterprise," the council said in a friend-of-the-court brief.

In an unsigned 5-to-4 opinion yesterday, the high court, without hearing argument, decided to send the case back for reconsideration in light of a decision it handed down last June 29 in the so-called Furnco case.

The majority said its message in Furnco was that an employer accused of a violation of the civil rights law need only "articulate some legitimate, nondiscriminatory reason" for his conduct. The 1st Circuit put "a heavier burden on the employer than Furnco warrants" by saying that the employer had to "prove absence of discriminatory motive," the majority said.

The majority acknowledged that "articulate" and "prove" have "more or less similar meanings," but said there is "a significant distinction."

In the dissenting opinion, Justice John Paul Stevens accused the majority of drawing a "novel" and "illusory" distinction that the curt itself rejected in the Furnco decision.

In Furnco, Stevens recalled, the justices - including himself - said it was the employers' burden to "prove" that he based his employment decision on a legitimate consideration. Moreover, he said, the 1st Circuit "virtually parrots" the Furnco opinion, in which "the words 'prove' and "articulate" were used interchangeably, and properly so."

Both verbs describe a defendant's burden in a trial context, Stevens wrote. Joined by Justice William J. Brennan Jr., Potter Stewart and Thurgood Marhsall, he added: