His voice stilled by illness, Paul McDevitt wrote out the words of gratitude he wished he could say aloud during a June ceremony in South Boston, where a building housing a program for low-income children was renamed McDevitt Hall, Home of The Paraclete Center.

“Long ago, I was taught that man is composed of three parts, physical, mental, and spiritual,’’ his wife, state Auditor Suzanne Bump, read on his behalf as he sat and listened. “I was taught that we had to pay attention to, to nurture, all three parts.’’

As a teacher, elected official, volunteer, and business founder, Mr. McDevitt spent decades lending assistance to everyone from high school students to the homeless and those struggling with substance abuse. He did so after bursting onto Boston’s political scene nearly 50 years ago, when at 25 he became the youngest person ever elected to the Boston School Committee. Two years later, he liked to joke, he was “the youngest incumbent ever defeated for reelection.’’ He went on to serve on the boards of numerous nonprofits, serve thousands of meals to the poor, and found Quincy-based Modern Assistance Programs.

Yet after listening to the praise others offered during the Paraclete Center ceremony, he gave thanks for a life “enriched by other people. Each one of you today is that other person. And I hope that I have been that person for you.’’

Mr. McDevitt, who had been on the center’s board and also had chaired the board for Project Bread, died Monday in his South Boston home of cancer of the vocal cords. He was 74 and divided his time between homes in South Boston and Housatonic.

Within Greater Boston’s substance abuse recovery community he held a special place, having shed the anonymity afforded by Alcoholics Anonymous — an organization he steered many to over the years. His death notice noted that he had been “sober one day at a time for 38 years.’’

“Paul McDevitt, you made a huge difference in my life, to be able to be in the position I am in today,’’ Boston Mayor Martin J. Walsh, himself a recovering alcoholic, said at the June ceremony. “I want to thank you for everything you have done.’’

A longtime friend of Mr. McDevitt — someone who still stands by the anonymity many in recovery embrace — was equally grateful. The friend recalled that upon taking initial steps toward giving up alcohol 21 years ago, “my head was as scrambled as when I was drinking. Paul said, ‘Do me a favor and come to a meeting.’ ’’ And that, the friend said, set him on the road to sobriety.

A willingness to help one person at a time, one conversation at a time, defined Mr. McDevitt as he built Modern Assistance Programs, said Marie Downey, who formerly worked for him. The agency has worked with unions and businesses to create employee assistance programs that address substance abuse, stress, grief, and other issues.

“He was never a salesperson,’’ Downey said of Mr. McDevitt, whom she described as more apt to forge work contacts through conversations with those he knew in the leadership of unions, for example.

Robert Banks, a former president and business agent of Ironworkers Local 7, and training director of its apprenticeship program during the Big Dig, said Mr. McDevitt helped set up innovative counseling programs for the union and added: “I don’t think we could ask for anything more than we got from Paul.’’

Mr. McDevitt always “led with his heart,’’ Downey said. “I don’t want to say he was one of a kind, because Paul would say he wasn’t. But he was living his life the way all of us could live our lives — by caring about one another.’’

The second of five children, Paul Francis McDevitt grew up in Dorchester. His father, James, was a state representative and a child welfare caseworker before becoming the attendance supervisor for the Boston Public Schools. His mother, the former Agnes Dunn, was a librarian.

Mr. McDevitt graduated from Boston College High School and Boston College, and “he would tell you that he was a highly indifferent scholar,’’ his wife said, “but he formed very deep, lifelong relationships with some of the Jesuits who taught him. He admired their intellect, their spirituality. He loved the commitment of service to others. Those are values that he cherished.’’

He initially considered studying law, but instead became a high school teacher in the Boston Public Schools, and years later received a master’s in education counseling from the University of Massachusetts Boston.

Mr. McDevitt previously was married to the former Patricia Riley, with whom he had two sons.

After emerging from a large number of School Committee candidates to win a seat in 1967, he fell short while seeking reelection in 1969. He also tried unsuccessfully to rejoin the School Committee in 1979.

In the meantime, Mr. McDevitt’s work included serving as the Metropolitan District Commission’s liaison to the state Legislature, where he met Bump, who was then a legislative aide. They married in 1980 and she went on to serve in the House and in Governor Deval Patrick’s Cabinet as secretary of labor and workforce development before being elected auditor in 2010.

“When I met him he was active at the Paulist Center and was cooking and serving at their Wednesday night Supper Club, open to the poor and homeless,’’ she recalled.

“One of the things that everybody takes from Paul is the fact that he was such as storyteller,’’ she added. “He understood the power of story — of parable particularly — to help people understand certain truths, and particularly truths about themselves. When you help somebody to overcome an addiction or a mental illness, you are helping them achieve a profound change within themselves, and also within their relationships with other people and within their community. And he just had such an exceptional gift for doing that.’’

In addition to his wife, Mr. McDevitt leaves two sons, Neil of Housatonic and Andrew of Attleboro; two sisters, Catherine Lent of Mount Kisco, N.Y., and Marie Biggs of Lake Forest, Ill.; a brother, Daniel of Quincy; and two grandsons.

A funeral Mass will be said at 10 a.m. Friday in Dorchester in St. Teresa of Calcutta Church, the former St. Margaret Church.

In a blog post several years ago, Neil recalled an occasion when a young man seeking advice mentioned to Mr. McDevitt “that he wouldn’t be able to go to UMass that year because he didn’t have the tuition. My father asked how much he was short. The guy said, ‘One thousand dollars.’ My father, who is not wealthy himself, wrote him a check in that amount.’’

Such generosity was hardly an isolated incident. Mr. McDevitt “didn’t care about hanging onto his money,’’ Neil added in an interview. “He was more interested in helping people realize their hopes and dreams.’’

Bryan Marquard can be reached at bryan.marquard@ globe.com.