Hagerty was an imposing figure who stood over six feet tall. According to perennial Socialist presidential candidate Eugene Debs, “he would command attention anywhere. On the rostrum he is a striking figure, and when aroused is like a wounded lion at bay. He has ready language, logic, wit, sarcasm, and at times they roll like a torrent and thrill the multitude like a bugle call to charge.” Debs would know; he had a history with Hagerty. Just a few months after Hagerty arrived at his new parish in New Mexico, where he served as the assistant rector, he left to attend a labor convention in Colorado. There he would share a stage with Debs, debating local clergy on labor issues. The two went on to tour a number of mining sites in the state, trying to drum up support for the American Labor Union (Hagerty would go on to be the editor of Voice of Labor, the official publication of the ALU) and the Socialist Party of America. The Archbishop of Santa Fe, Peter Bourgade, did not care for Hagerty’s extended absence—nor the politics that occasioned it. So he disowned him. Freed from his pastoral duties, Hagerty became an itinerant preacher for socialism, debating and stumping on behalf of the Socialist Party. By 1903 he was a regular on the political circuit, speaking at rallies before huge crowds.

Charismatic, combative, and silver-tongued, Hagerty earned his fair share of detractors. Conflicts with the Catholic hierarchy made him an easy target for them; accusations that Hagerty left both the priesthood and the church were powerful tools for enemies of the working-class movement. His Catholic credentials, along with those of his comrade, Fr. Thomas McGrady (also a member of the Socialist Party of America), or his Canadian socialist analogue, Fr. Eugene Cullinane, CSB, were important in appealing to the large contingent of Catholic working people who were also hearing from clergy and bishops that sympathy strikes and enforcing the picket line were immoral.

The Cincinnati Enquirer, for example, reported that Hagerty voluntarily resigned from the priesthood in 1902, a charge he forcefully denied in a letter to the International Socialist Review. “I am as much a priest to-day as I ever was,” he wrote. “I have not separated myself from the communion of the Catholic Church; and I hold myself as much a member thereof as the Pope himself.” As for the anti-socialist statements of the church, present both in papal encyclicals and American bishops’ denouncements of the Socialist Party and labor strikes, Hagerty referred to the “socialist” John Chrysostom, and said that members of the hierarchy exceed their authority when they “oppose a movement whose highest purpose is the industrial liberation of the wage slaves of the world.”

A year after the Cincinnati Enquirer accusation, Montana’s Butte Miner said Hagerty was excommunicated. Hagerty again replied with characteristic venom to a crowd in Butte itself, and a few months later he offered $1,000 to anyone who could prove he was no longer a priest, equivalent to well over $25,000 today. There is no evidence anyone ever took Hagerty up on the offer.

Hagerty often drew on Catholic imagery in his pamphlets and speeches. Describing the life of an unemployed family man in his pamphlet “Economic Discontent and Its Remedy,” he wrote, “The gaunt faces of his children stamp themselves into every fibre of his memory, like the face of the Christ upon Veronica’s towel, as their father drags his weary steps along labour’s way of the cross day after day in search of work.” In the same pamphlet, Hagerty goes on to suggest the conditions of capitalism are enough to dissuade working people from any belief in God. “Too often another Golgotha is encompassed when the faithful wife or the loving child, breaking down under privation, falls an easy prey to some current malady and, mayhap, is buried in a pauper’s grave the while the stricken husband or father can only cry out, in that world-old plaint of oppressed humanity, ‘Eli, Eli, lama Sabachthani’—My God, my God, why hast Thou forsaken me?”

He could have added more than just the unemployed family man, recalling scenes like those depicted in Upton Sinclair’s 1906 novel The Jungle. The condition of working women, too, was a scene of many Golgothas, not least rape and sexual exploitation. Immigrants, especially from China, were routinely used to prevent worker solidarity, and as a source of cheap and disposable labor. Black socialists, including preachers like Rev. George Washington Woodbey, powerfully expressed the continued oppression of black Americans as the United States industrialized—something Hagerty himself utterly failed to recognize, imbibing and reproducing the pervasive whiteness of the labor movement.

Without dismissing such blind spots, Hagerty’s contribution to the radicalization of the labor movement remains unique. Despite being one of the Socialist Party’s most dedicated and active members, Hagerty became frustrated with the reformist tendencies of what he called “sidewalk socialists” in the party. Eventually his frustrations boiled over. After hurling a string of insults at party leaders, the chairman of a party meeting broke his gavel—hardly enough to stop Hagerty—and a group of socialists had to forcibly remove the proletarian priest from the stage. Now Hagerty could add major socialist officials to the list of authorities who disowned his radicalism.

Another vehicle for the struggle was needed. Hagerty and a group of radicals met right after the New Year in 1905 to draw up a manifesto. Naming class struggle as a fundamental and “irrepressible” conflict in society, the manifesto called for a collective movement without party affiliation. Hagerty was credited with writing most of it.

Later that summer, a veritable "who’s who" of American labor responded to the manifesto and gathered at Brand’s Hall in Chicago: Lucy Parsons, a radical organizer whose husband Albert was hanged among the Haymarket martyrs; James Connolly, an Irish worker who returned to Ireland to help organize the Easter Rising of 1916, after which he, too, would be executed; Mother Jones, whose early Catholic faith had put her on the road to radicalism; “Big Bill” Haywood, who fled to a young USSR while out on bail in 1921 and took up an advisory role in Lenin’s government; Eugene Debs, arguably the most significant socialist in American history. And, of course, among several other giants of the working class was Father Thomas J. Hagerty. Together, they founded the Industrial Workers of the World.

Perhaps Hagerty’s most lasting contribution to the American workers’ struggle was drafting the preamble to the IWW’s constitution. “The working class and the employing class have nothing in common,” it begins, a far cry from the “class harmony” advised by Rerum novarum. “There can be no peace so long as hunger and want are found among millions of the working people and the few, who make up the employing class, have all the good things of life.” He was frustrated by those he derided as “slowcialists,” who aimed to create a more just society through legal means and electoral politics. “Dropping pieces of paper into a hole in a box never did achieve emancipation for the working class, and in my opinion it never will,” he once argued. Instead Hagerty dreamed of “One Big Union,” a unified struggle of working people to meet the challenge of a unified capitalist class. To illustrate the idea, he drew up a chart, known as “Hagerty’s Wheel,” showing how unions in diverse industries could be linked by converging on a single point that would help bolster and defend weaker industrial branches. The IWW still uses an updated version of it.