'EXCUSE ME," the polite young man or woman in the long black cloak will say, "would you like to make a donation to our Church to help us with our programs for young people?" If you refuse, he or she will smile and turn away to someone else passing on the street. If you stop, and if you give some change and ask about it, you'll begin to hear about the Process, the Church that these evangelical fundraisers on various sidewalk stations in busy parts of Boston and Cambridge belong to. You'll be offered (for $2.50) one of their glossy, color-covered, large-print paperback books to help you understand more of what the Process is about and you may get an invitation to visit "The Cavern," a coffee-house in the basement of their roomy home at 46 Concord Avenue in Cambridge.

TO THE members of this Church, "Process" means "pro-cessation," or "for the end" -of the world. Process, the "Church of the Final Judgment," was founded in 1963 by a man named Robert DeGrimston and his wife. DeGrimston's photograph appears inside several of the Process books which were "recorded" by DeGrimston himself. In the photographs, he has, like many of the men in the Church, neat shoulder-length hair and a trimmed moustache and beard; he also has the elevated gaze of a solemn visionary.

Today, DeGrimston is the "spiritual figurehead" of the Church. According to one Boston "Processean," he and his wife are no longer affiliated with a chapter but are traveling, stay-in contact with the four present Process chapters, and visiting them on occasion.

The Church was based in London for its first five or six years until, following a series of ineffectual lawsuits against them, the Processeans lost a suit filed against their operation of a basement coffee house in violation of city zoning laws. This lost suit was taken as a sign that the Church should leave London, and the London chapter was closed. But the Boston Processeans expect the London chapter to be reopened some day.

In January 1970, three London Processeans arrived in Boston; they were later joined by a few others in founding the first American chapter. In comparison to the original London chapter, the Process in Boston has thrived remarkably; apparently there is still something in the American climate to nourish transplanted dissenting religions. At one point the Boston chapter had 150 members in its community, many more than the Church ever had in London. They have since sent out members to begin chapters in Chicago, Toronto, and New Orleans, so that the number in this area is now set at about 100 members, thirty of whom are "in black," and fifteen of whom are "Inner Processeans," living at 46 Concord Avenue. One Inner Processean who was part of the London chapter and who went through, with other London Processeans, a period of international wandering before re-establishing the Church in Boston, prefers America to England. "We feel it is more open."

THE FINAL Judgment, according to the belief of the Church, will bring "the purifying presence of fire in the world... After the ashes of the end will arise the new beginning... love and unity and giving as opposed to fear and isolation and war." Processeans do not know exactly when the end will come, except that it will be sometime within the next twenty-nine years, before the next turn of the century.

Brother Christopher, who was a student at M. I. T. before he joined the Process, explains that "the people who cling to the structures of humanity, guilt, fear, a need to be superior, a need to blame another person, a need to make an excuse for something we've done, will be destroyed at the Final Judgment.... Those who will be saved are the people who meet their fears- accept them first of all-and see that when we first choose to be afraid, we can equally be unafraid. By doing the things, we're most afraid of doing, we can be invulnerable."

THE HEAVY black smoke of burning incense pours out of the door to a front room at 46 Concord Avenue on Saturday nights at 7, when the weekly Process Sabbath Assembly, their public religious service, begins. Inside the room, the pale skin of a few babies shows up sharply in the candle-light against the black clothing of the women who hold them. Over and over, the worshippers sitting on cushions around the floor sing to the accompaniment of three guitars a hymn that stresses the unity of the members of the Church. At one end of the room, hung on a deep purple drape, is a silver cross; at the other end, over a black curtain, is a red representation of the horned goat of Mendes, a symbol of Satan.

Those who don't know the liturgy of the Sabbath Assembly are given, as they enter, a booklet that contains a printed outline of the service, with the appropriate invocations, responses, and indications of the places where sermon-like talks are given by "Superiors" of the Process.

Two large dogs, one black, one white, are led into the room on leashes. Several men, Superiors, enter in black cloaks that have special colored panels in them. A gong is sounded to begin the Assembly.

A recurrent expression in the liturgy of the Sabbath Assembly is "An end-and a new beginning." At certain times the Superior reciting the liturgy concludes his passage with "As it is," to which those assembled reply "So be it": a greeting and reply Processeans often use during the course of the day that corresponds roughly to "How are you," and "Fine thanks." At several points in the service, the Music Officer announces the number of the hymn, and the Assembly sings the words of the hymn to the kind of simple, logical melody that, like the melodies of many hymns in other churches, is easy for someone who has never heard it before to sing along with.

There is a time near the end of the service when those who are not members of the Church of the Final Judgment are encouraged to come forward and kneel to be received as Acolytes in the Church.

The Sabbath Assembly is subdued and solemnly conducted, but at one point a Superior speaks informally to the Assembly, making small jokes, inviting responses from those on the floor around him. As the liturgy proceeds, examining in turn the gods Jehovah, Lucifer, Satan, and Christ, a sense of community seems to build in the Assembly; when the service is over, the Superiors of the Church leave first, and others follow, happy and relaxed. Like many other religious ceremonies, the Sabbath Assembly of the Process seems to leave its participants with a sense of pleasant relief and fulfillment.

ALL THE members of the Church of the Final Judgment are organized into a hierarchy-there is no congregation of Church members who exist outside it, though there are many who follow the activities of the Process from outside the Church.

Those who are received into the Church as "Acolytes" can become "Initiates" after a period of a few weeks. A tithe, the donation of one-tenth of the member's income to the Church, is a requirement for becoming an Initiate.