In the midst of the heated debate over immigration and the tug of war between the White House and federal judges across the country, one phrase continues to epitomize the pro-immigrant argument: “We are a nation of immigrants.”

This slogan is repeated constantly on television, in newspapers across the country and in fiery speeches delivered on the Senate floor. It originated well before the fierce debate over illegal immigration or Syrian refugees, coming instead from a book written by the most famous man who ever lived in Brookline, Massachusetts.

John F. Kennedy was not finished writing his novel A Nation of Immigrants before his assassination in 1963, leaving his brother, Attorney General Robert F. Kennedy, to publish it posthumously, according to the website of the John F. Kennedy Library and Museum. Kennedy first published A Nation of Immigrants as an essay for the Anti-Defamation League’s (ADL) series on immigration and anti-semitism in 1958, when he was still a Massachusetts Senator. In 1963, he addressed the ADL and famously proclaimed, “We are a nation of immigrants.”

According to OnTheIssues.org Editor-in-Chief Jesse Gordon, Kennedy drew examples from American and world history as evidence towards his key argument that “Americans are all immigrants and therefore excluding certain immigrants from certain nations is nothing more than racism.”

Kennedy foresaw the ballooning debate over immigration via our Southern border, dedicating significant portions of his novel to Mexican immigrants. He related their travails to his own Irish ancestors, who faced discrimination from groups like the “Know-Nothing Party” which was formed in opposition to Irish immigration.

“The same things are said today of Puerto Ricans and Mexicans that were once said of Irish, Italians, Germans and Jews: ‘They’ll never adjust; they can’t learn the language; they won’t be absorbed,’” Kennedy wrote in A Nation of Immigrants.

According to OnTheIssues.org, Kennedy covered an array of historical trends and topics involved in the discussion of immigration: anti-immigrant political parties, civil rights, persecution versus economic immigration, Constitutional law, families, isolationism vs. interventionism, jobs and freedom of worship.

“Perhaps our brightest hope for the future lies in the lessons of the past. As each new wave of immigration has reached America it has been faced with problems, not only the problems that come with making new homes and new jobs, but, more important, the problems of getting along with people of different backgrounds and habits. Somehow, the difficult adjustments are made and people get down to the tasks of earning a living, raising a family, living with their neighbors, and, in the process, building a nation,” Kennedy wrote.

Kennedy wrote the book to push for pro-immigration reforms in the 1960s, but his chief objectives differ from many of the books published by current politicians. A Nation of Immigrants was a dissertation on Kennedy’s long-standing moral values, not necessarily a reaction to a certain crisis or debate at the time. A Nation of Immigrants was intended to stand the test of time.

Kennedy wrote several political books besides A Nation of Immigrants. In 1940, he published a lengthened version of his senior thesis from Harvard, which criticized England’s tepid policy of appeasement towards Nazi expansion in Europe, titled Why England Slept.

Kennedy was awarded the Pulitzer Prize for Biography with his 1957 novel, Profiles in Courage, the same year he arrived in the U.S. Senate. However, according to “The Washington Post” and other publications, his contributions were called into question in 2008 after ghostwriter Ted Sorensen admitted that he wrote most of the novel himself. Sorensen also helped Kennedy with some of his most famous addresses, but Kennedy was a known writer and someone who knew, and captured, the power of the written word.

A Nation of Immigrants displayed the importance of Kennedy’s educational background in his thoughtful analysis of history, as well as his youthful, unabashed idealism. His legislative legacy may have been small in comparison to his expansive goals, but his founding contributions to the modern debate over immigration cannot be understated.

In an era where vitriol lines both sides of the aisle and corrodes every debate we have, Kennedy’s uplifting, positive conviction and dutiful confidence in American values is truly missed.