Early reactions to Pope John Paul's massive encyclical Laborem Exercens (Performing Work) have generally been favorable, with some reservations.

Issued Tuesday, the third encyclical of John Paul's pontificate calls for fuller participation of workers in management and the fruits of production and says labor unions are an "indispensable element" of modern society.

Msgr. George Higgins, one of the pioneers of the church's involvement in social justice who is now teaching at Catholic University, called it "a fairly radical document" in that the pope "absolutely rejects the notion of the absolute right to private property".

The thing that impressed the Rev. Phillip Land, for years a staff member at the Vatican's Commission on Justice and Peace, was the pontiff's "extraordinary definition of trade unions . . . He said that 'History teaches . . . that trade unions are an indispensable element of social life.' "

"In my 50 years of reading documents, and helping to prepare them, it's never been said so strongly," said Land, who is now on the staff of the Jesuit-based social justice think tank here, the Center of Concern.

He added, " . . . . That's being said in a moment in which in the United States, a lot of big businesses are trying to wreck the trade unions. It's just an extraordinary support for unions . . . . I'm sure it reflects his own experience in Poland."

"With few exceptions, it strikes me as a brilliant piece of work," said Michael Novak of the American Enterprise Institute, thus confounding both Land and Higgins, each of whom predicted disapproval by conservatives, of which the AEI is a bulwark.

His immediate reaction, based on newspaper accounts and excerpts from the 99-page document, was that John Paul II "has advanced the thinking of the church's social documents on capitalism and socialism . . . When he addresses capitalism, he has a bit more recognition of its flexibility, of its different forms."

The major points of the encyclical, which was delayed four months by the attempt last May on thepope's life, flow out of the central theme that God, in giving man dominion over the earth and directing him to subdue it, established work as "a fundamental dimension of human existence on earth."

Developing a philosophy of work from these Biblical roots, the pontiff takes these views:

* "Capital should be at the service of labor and not labor at the service of capital."

* A just wage for the worker is the ultimate test of whether any economic system is "functioning justly."

* Women who wish to work outside the home should have the opportunity on an equal basis with men, without discrimination. But societies should make it possible for mothers who want to stay home with their children to do so, either by guaranteeing an adequate wage to the husband or by family allowances geared to the number of children. The work women perform as homemakers should be valued equally with other kinds of work.

* Because of the complexities of international economics, developed nations, international organizations and multinational corporations are in effect "indirect employers" of workers in the Third World. As such they are responsible for economic arrangements to provide a living wage in the poor countries.

* Neither "rigid capitalism nor socialism" guarantees that workers will be treated fairly. Worker's rights are most likely to be assured by sharing the means of production so that each worker, no matter how menial his job, may "consider himself a part-owner of the great workbench at which he is working with everyone else."

"Performing Work" builds on the 90-year tradition of encyclicals dealing with social justice, citing the arguments of John Paul's predecessors and adding his thoughts. Among those who have had a chance to read the document, there is disagreement on its significance.

"I didn't see anything in it that really excited me or struck me as new," said Sister Ruth Nieland of Network, an unofficial organization of Catholic sisters devoted to lobbying on social justice issues. "It's nice he said what he said instead of opposing certain things, but it seemed to me that he just reiterated what has been said in the past."

The Rev. Jan Schotte, secretary of the Vatican's Justice and Peace Commission, said at the Rome press conference releasing the document that the encyclical was a synthesis of statements the pope had made on his many travels.

Nieland, whose organization has been particularly vocal on behalf of women's rights, was relatively neutral on the three or four paragraphs devoted to women. "I don't see that it made a statement, really," she said.

Feminists have criticized earlier speeches in which John Paul said women's place was in the home. The call for an end to discrimination against women in the workplace pleased feminists, but some eyebrows were raised at the next statement: "The true advancement of women requires that labor should be structured in such a way that women do not have to pay for their advancement by abandoning what is specific to them and at the expense of the family . . . ."

Women are twice portrayed as responsible for child-rearing; men are pictured only as breadwinners.

"That's where he's at," commented Land. "It remains to be seen whether he can change."

Msgr. Francis J. Lally, secretary for Social Development and World Peace for the U.S. Catholic Bishops' Conference called the encyclical "a real shot in the arm for the whole social justice cause . . . . I think it will have a long range effect. It will be studied as a new projection of the message. It will help people think about work."

The encyclical is distinctive for its more personal style and John Paul's departure from the use of "we." "It's very personal. I'd be willing to bet that he wrote it himself," said Higgins.

Land predicted that the encyclical, with its strong support of organized labor, "will be heartening to all the people trying to form trade unions in all the places where you have security states."

While the pontiff includes managers, administrators, intellectuals and those concerned with high technology in his embrace of workers, Land feels the document "puts him squarely at the side of the people at the bottom of the heap . . . What he is really talking about is working-class people."