He died of complications from lung cancer, said his son, William Kristol, the founder and editor of the conservative Weekly Standard magazine.
The elder Kristol founded and edited magazines such as Encounter and the Public Interest that targeted an elite audience of political, social and cultural tastemakers. In addition to his professorship at New York University, he advanced his ideas through monthly opinion pieces in the Wall Street Journal and a fellowship at the American Enterprise Institute think tank. He was for many years an editor at Basic Books, a small but distinguished publisher of works in social science and philosophy.
Karl Rove, a Republican strategist who advised former President George W. Bush, called Kristol an "intellectual entrepreneur who helped energize several generations of public policy thinkers."
Through his editing, writing and speaking, Kristol "made it a moral imperative to rouse conservatism from mainstream Chamber of Commerce boosterism to a deep immersion in ideas," Rove said. He added that Kristol helped create a synthesis of Cold War Democrats and Reagan White House anti-communist hawks, which proved decisive in influencing foreign and military policy in the 1980s.
Kristol and his historian wife, Gertrude Himmelfarb, along with a group of sociologists, historians and academics including Norman Podhoretz, Nathan Glazer, Richard Pipes and for a while Daniel P. Moynihan, emerged in the late 1960s and '70s as prominent critics of welfare programs, tax policy, moral relativism and countercultural social upheavals they felt were contributing to America's cultural and social decay.
His father was an immigrant garment worker from Eastern Europe, and Kristol grew up under humble circumstances that shaped his beliefs. "Those who have been raised in poor neighborhoods -- the Daniel Patrick Moynihans, Edward Banfields, Nathan Glazers -- tend to be tough-minded about slums and their inhabitants," he told the New York Times.
Middle-class sociologists, he said, "are certain that a juvenile delinquent from a welfare family is a far more interesting figure -- with a greater potentiality for redeeming not only himself but all of us -- than an ordinary, law-abiding and conforming youngster who is from the very same household."
Kristol had grown dismayed by the fragmentation of the Democratic Party over the war in Southeast Asia and remained a vigorous defender of a strong military to combat communist threats. He championed a steady focus on economic growth that gives "modern democracies their legitimacy and durability" but cautioned against running deficits. He popularized supply-side economics, long considered a fringe belief that tax cuts would lead to widespread financial prosperity. Supply side became a leading conservative cause in the 1980s and influenced the Reagan administration's tax policy.
Kristol and many of his colleagues were dubbed neoconservatives, a term introduced by social critic Michael Harrington to describe the rightward turn of onetime liberals such as Kristol, whose extraordinary political odyssey had taken him from Depression-era socialist to anti-communist Cold Warrior and Vietnam War hawk.
While Harrington's use of neoconservative was not intended as a compliment, Kristol embraced the term and became its widely accepted godfather. A cover story on Kristol in Esquire magazine in 1979 helped legitimize him as the leader of a full-fledged movement, even as he played down the idea that such a formal faction existed.
"We are not a movement," he once said. "There has never been a meeting of neoconservatives." He called it an "intellectual current" that came to prominence after a "gradual evolution."
Kristol found his public profile raised greatly by the Reagan presidency, when many neoconservatives, such as Paul Wolfowitz, William Bennett, Richard Perle and Elliott Abrams, began to occupy administration jobs and found themselves in positions of influence over domestic, diplomatic and defense policy. Neoconservatism also formed the core beliefs of many advisors to George W. Bush, who gave Kristol the Presidential Medal of Freedom, the nation's highest civilian honor, for helping set "the intellectual groundwork for the renaissance of conservative ideas in the last half of the 20th century."
Cultural and intellectual historian Paul Boyer of the University of Wisconsin called Kristol "one of those who helped make conservatism intellectually respectable" in the 1960s when New Deal liberalism was still a dominant political philosophy. Conservatives, Boyer said, had long been marginalized as backward-thinking scolds who denounced social policies created by the central government.
Jacob Heilbrunn, author of "They Knew They Were Right: The Rise of the Neocons," said Kristol's thinking "played a big role in reshaping the Republican Party."
"He told traditional conservatives you need to accept New Deal and accept the achievements of liberalism," Heilbrunn said. "You don't try to roll it back but stop it from expanding further. He and other neoconservatives of his generation, including Norman Podhoretz, had a galvanizing effect on the Republican Party, and were viewed as heretics and ostracized by a mainstream intellectual establishment that was overwhelmingly liberal. Irving Kristol and Norman Podhoretz come out of that radical and liberal tradition and they were seen as apostates."
Irving William Kristol was born Jan. 22, 1920, in Brooklyn, N.Y., attended City College of New York and served in the Army during World War II.
Besides his son and his wife of 67 years, whom he met at a Socialist League meeting, he is survived by a daughter and five grandchildren.
Bernstein writes for the Washington Post.