He makes about 2,000 phone calls a year. He speaks two or three times a month at various houses of worship within a 100-mile radius of his Chatsworth home. And he books lunch or dinner engagements with any clergy member of any faith who will give him 90 minutes of his undivided attention.
To date, he counts more than 500 meals with individual priests, rabbis and ministers.
But Schwartzbart isn't on a religious mission. Rather, he said, "I am determined to keep the United States from becoming a theocracy."
To accomplish this, the 84-year-old retired Rockwell engineer and metallurgist consultant works tirelessly as president emeritus of the San Fernando Valley chapter of Americans United for Separation of Church and State, a national education and advocacy organization of 75,000 members that "devotes 100 percent of its time and resources to church-state separation."
The group meets quarterly at varying Jewish and Christian sites. At its most recent meeting on Jan. 28 at Temple Judea, the San Fernando Valley chapter featured as its guest speaker Nick Matzke, an expert in debunking "intelligent design" claims.
A member almost since its establishment in 1947, Schwartzbart did not become active until 1994, when Pat Robertson was "scaring the hell" out of him. At that time, he founded the San Fernando Valley chapter, which quickly became the largest and one of the most active of the organization's 70-some local chapters.
Strictly a volunteer, he served as president until two years ago. Now, as president emeritus, he retains his position as the one-man membership committee -- which he considers his most important duty -- as well as the sole speakers bureau representative.
From the first meeting on Oct. 5, 1994, Schwartzbart's single, unstoppable focus has been to make as many Americans as possible aware of what he considers the 16 most important words in the English language, the Establishment Clause of the First Amendment: "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof."
While his success is difficult to measure definitively, he claims to have enlightened a significant number of people.
"I'm persistent as hell; I never give up," he said, explaining that he calls himself Harry "Nase Shmate" Schwartzbart, translating the Yiddish as "wet rag." "Some of my very best friends won't take my calls anymore," he added.
He also laments that he has never succeeded in engaging any Orthodox rabbi in dialogue. The Orthodox, he said, primarily because of the voucher issue, side with the Robertson supporters.
Having discovered early on that his most useful tool is the telephone, Schwartzbart calls every person on his mailing list no less than once a year. The number has remained steady at about 2,000 names, with a turnover of about 5 percent each month.
A self-professed Luddite, Schwartzbart keeps all his contact information on 3-by-5 cards he arranges alphabetically in five long file boxes, meticulously logging every phone conversation, donation and even "do not call" request. His wife, Mary, backs up all the data on a computer.
"Harry is literally an organizational genius, and he was one even before anyone invented the Internet," said the Rev. Barry Lynn, executive director of Americans United. Lynn frequently dispatches Schwartzbart to other parts of the country to help volunteers establish new chapters.
In addition to his phoning, Schwartzbart speaks as often as possible. He says he requires five hours to do his subject justice. He's happy to talk that long or as little as five minutes.
Preferring to run a lean organization, he eschews fundraisers, but he does hold four general meetings a year. He also actively monitors Establishment Clause law violations and intervenes when necessary.
"Being a Jew" is Schwartzbart's short answer to what motivates him to do this work, maintaining that any Jew who does not support separation of church and state is an "idiot."
And while he admits to being raised Orthodox, he won't discuss his theological views, claiming they are irrelevant to his work in Americans United, which counts in its membership a cross-section of believers of all faiths as well as nonbelievers.
Pressed further, he explains that he was the first in his family to be born in the United States. His parents left Ukraine, escaping political persecution, and settled with their four children in Altoona, Pa., in 1921. Schwartzbart was born two years later.
While the United States has had its share of fundamentalists and religious extremists throughout history, Schwartzbart believes that "the religious right has a degree of political power unprecedented in this country."
He sees today's hot-button issues as women's reproductive rights, gay rights and the teaching of intelligent design. Additionally, sex, prayer in school and the flag remain continuing concerns.
Outside of Americans United, his only organizational commitment, Schwartzbart is devoted to his family. He has been married for 53 years and has three grown children.
Music is Schwartzbart's avocational passion. In fact, he met his wife while playing viola in the Altoona Symphony Orchestra, where she played the violin. Until about 10 years ago, they played string quartets in their house at least once a week.
Additionally, Schwartzbart is a staunch Shakespeare buff. He reads some of the Bard's work each day and has been diligently keeping a journal for the last two decades -- one for each year -- titled, "My Daily Shakespeare," in which he enters quotations pertaining to historic or personal events.
Schwartzbart's biggest worry is the future of Americans United in the San Fernando Valley, even though the current president is actively engaged.
"I am sorely afraid that when I am gone, the chapter will die," he said.
In the meantime, showing no signs of slowing down, Schwartzbart intends to keep working on behalf of Americans United.
"There's nothing that drives me harder. I do whatever I think it takes to help the cause," he said.
For additional information on Americans United, visit the San Fernando Valley chapter at www.ausfv.org, where you can read Schwartzbart's monthly commentaries, or the national organization at www.au.org.