Robert Jackson Supreme Court Justice Robert H. Jackson.

The late Justice Robert Jackson has long been revered by lawyers across the spectrum, not only because he was one of the court's best writers, but also because he personified the even-handed prosecutor that government lawyers aspire to become.

Much has been written about U.S. Attorney General William Barr and other Trump Justice Department officials who view Jackson as "the patron saint of the rule of law." Barr took dibs on Jackson's official portrait when he took office last year, and the antitrust division, which Jackson once led, has created something of a shrine in Jackson's honor, complete with Jackson memorabilia culled from the Library of Congress.

That veneration is not likely to change anytime soon. But an essay written by Jackson nearly 70 years ago has just surfaced, and it casts a new light on his views about religion.

The University of Pennsylvania Law Review published the essay, titled "The Faith of My Fathers." It was a personal account of his own upbringing in a family that respected the religion of others, but did not embrace religiosity.

"From the beginning, I was taught that the other man's relations with the infinite were none of my business," Jackson wrote. "My people detested all meddlesomeness in affairs of the spirit—and so do I … Intellectually I am and have always been an agnostic."

Jackson's family found the handwritten essay after his death in 1954, and in 2002 gave it to John Barrett, Jackson's biographer and professor at St. John's University School of Law.

Barrett held it for use in the biography, but decided that with the growth of Jackson's popularity, and changing views on the First Amendment's religion clauses, it was time to make it public.

"The essay contrasts with the way many justices recently and now, including some who have been major Jackson admirers, practice, speak about, and write about their religions and religion generally," Barrett said. "Jackson's separationist views also are quite different from how Free Exercise and Establishment Clause constitutional doctrines have developed."

The essay emerged as the Supreme Court hears arguments Wednesday in Espinoza v. Montana Department of Revenue, a church-state dispute. The government's brief in the case quotes Jackson briefly.

"In Jackson's living and in his constitutional judging, he gave religion its private space," Barrett wrote in an introduction to the essay. "He objected, however, and he read the Constitution as stating grounds on which to object when government sought to bring religion into public spaces."