In December 1967, the Reverend Martin Luther King Jr and the Southern Christian Leadership Conference announced the “Poor People’s Campaign” to demand basic economic and human rights, especially for people living in poverty. That campaign, led by Ralph Abernathy, took place in the spring of 1968, after King’s assassination.

Fifty years later, that vision was reborn with the formation of “The Poor People’s Campaign: A National Call for Moral Revival”. This reincarnation of the Poor People’s Campaign is led jointly by the Reverend Liz Theoharis, the co-ordinator of the Poverty Initiative at Union Theological Seminary in New York City, and the Reverend William Barber, the recent recipient of a MacArthur Foundation “genius” grant, whom Cornell West famously called “the closest person we have to Martin Luther King Jr”.

But this focus on titans of the leadership of social movements, especially the Civil Rights Movement, is misplaced. The iconic status of many civil rights leaders of the past often overshadows the myriad people who struggled, suffered and sometimes died in the movement.

Although he did not march on the front lines, Howard Thurman is one of those often overlooked heroes. He played a key role in providing the theological foundation for the Civil Rights Movement and helped to pave the spiritual path upon which King and others would tread.

As Thurman argued: “It was important that individuals who were in the thick of the struggle for social change would be able to find renewal and fresh courage in the spiritual resources of the Church.”

His efforts demonstrate that effective social action requires a community working together for change that is bonded together by a coherent ethical, theological or philosophical foundation.

Although Thurman was a nationally and internationally recognised figure during his lifetime, today, if remembered at all, he is known as a mentor to King, including his likely influence on King’s merging the religion of Jesus with Gandhi’s nonviolent resistance.

As the leader of a small group of African-Americans on a speaking tour in India, Sri Lanka and Burma in 1935-36, Thurman was the first African-American to meet Mahatma Gandhi and incorporate Gandhi’s insights — such as satyagraha or “soul force” — into his theology. Thurman and Gandhi shared a deep reverence for the teachings of Jesus and the belief that modern Christianity had deserted his true message.

After his meeting with Gandhi, Thurman undertook “an exploration of the problems that arise in the experience of people who attempt to be Christian in a society that is essentially un-Christian”. This led him in 1949 to publish his best-known book, Jesus and the Disinherited, which served as an inspiration for many civil rights leaders (Martin Luther King often carried this classic work).

In that book, Thurman argued that the religion of Jesus was born in the context of a people suffering persecution and oppression. Over the centuries, however, Christianity became the established religion of nations whose use of power and violence violated the essence of his message. Thurman realised that Jesus, a poor 1st-century Jew, spoke to others who, like him, were poor, oppressed, disinherited and dispossessed — those with their “backs constantly against the wall”. By highlighting Jesus’s message to the oppressed, Thurman made the teachings of Jesus again relevant for the struggle for civil and human rights.

Like Gandhi, who was himself deeply influenced by Leo Tolstoy’s book The Kingdom of God is Within You, Thurman insisted that spiritual transformation must be the foundational first step that leads to all other transformations of self and society, including concrete social action on behalf of the poor and oppressed.

As a result, Thurman regularly invoked Jesus’s parable of the prodigal son, which celebrates a father’s welcoming his wayward son back into the family with love, compassion and forgiveness, as well as the Good Samaritan, which illustrates how one should treat fellow human beings, no matter who they are.

For Thurman, the parable of the Good Samaritan was personal because he attributed part of his own success to a mysterious “Good Samaritan” to whom he dedicated his autobiography: “To the stranger in the railroad station in Daytona Beach who restored my broken dream sixty-five years ago.”

Thurman was leaving home to attend one of the two high schools in Florida that at that time accepted African-American students, but he did not have the funds to take the train with his luggage. Then a “Good Samaritan” appeared and paid his fee.

Thurman observed that we are all indebted to people whose names we do not know and whose faces we sometimes do not see. He believed that such indebtedness was in fact a powerful force, that our knowledge of being indebted to God and being indebted to other human beings should fill us with a sense of gratitude for these blessings and, as a result, a desire to “pay it forward”, to help others just as we have been helped.

Thurman contended that an existential encounter with the teachings of Jesus must lead to concrete action in the world, including a profound moral obligation to reflect, decide and act accordingly, whether by working for civil and human rights, promoting justice amid oppression, seeking peace among those who advocate for war or, in the words of Jesus, proclaiming good news to the poor, release to the captives and liberation of the oppressed.

Thurman’s vision provides a much needed corrective in an era often dominated by political tribalism, in which opinions on various issues closely correlate with the sometimes fluctuating positions of the political party with which people identify, including significant changes in moral values.

These changes in ethical values have profound implications for public discourse and for social actions, since shifts in attitudes and values lead to shifts in actions.

When Donald Trump, for example, calls the news media “the true enemy of the people” or encourages chants that call for his political opponents to be “locked up”, those words have consequences. Such inflammatory rhetoric, where cruelty is the point, stokes fear, anger, hatred and division.

As even the President knows, incendiary rhetoric not only begets more incendiary rhetoric, it also can lead to violent actions — hate crimes have spiked over the past two years, including a 57 per cent increase in anti-Semitic incidents.

In today’s contentious, toxic and increasingly violent environment, Thurman’s vision reminds us that our principles should not vacillate with shifting political winds. Our beliefs and corresponding actions should be consistent, and they must be based on a solid, philosophical or religious foundation, which, for Thurman, was the actualisation of the inner presence of God outwardly in one’s words and deeds. Although Thurman looked primarily to the example of Jesus, he also pointed to other people as moral exemplars, those who had “walked with God”, such as Gandhi, Buddha, Plotinus and Meister Eckhart.

In addition, societal transformation must begin with an inner, personal transformation of individual human beings, which is the reason Jesus, Thurman argued, “again and again came back to the inner life of the individual”. This transformation of individual human beings creates a community — what was called in the Civil Rights Movement a “Beloved Community” — that is dedicated and active in social transformation based on their core beliefs and in response to the human need that surrounds them.

For Thurman, like Gandhi before him and King after him, “nonviolence — what Gandhi called ahimsa, which for both Gandhi and Thurman is analogous to “Christian love” — is not merely an abstention from violence. Instead, it is a positive force working to effect positive social change: actively wanting and working for the wellbeing of all people.

And just as Thurman’s philosophy was evident during the Civil Rights Movement in the 1960s — for instance, the 1963 Birmingham Civil Rights Movement’s “Ten Commandments” — it has found worthy successors in such present movements as the Poor People’s Campaign led by Barber and Theoharis.

Thurman knew that social justice would never be completely achieved, but he believed that human beings should “really work at it” because, he argued, despite all of the difficult obstacles one faces, individual people can make the world a more decent and humane place. He ends with this plea, which remains excellent advice today: “Let’s try it and see.”

• David B. Gowler is the Dr Lovick Pierce and Bishop George F. Pierce chairman of religion at Oxford College of Emory University and the author of The Parables after Jesus: Their Imaginative Receptions across Two Millennia