Peter Gay, who has died aged 91, was a German-born historian who wrote groundbreaking books on the Enlightenment, the Victorian middle classes, Sigmund Freud, the culture of interwar Germany and the cultural situation of Jews in the country.
Gay, a refugee from Nazi Germany, devoted his long career to exploring the social history of ideas, a quest that eventually took him far afield from his original area of specialisation, Voltaire and the Enlightenment.
His Voltaire's Politics, published in 1959, was followed by the monumental two-part study The Enlightenment: An Interpretation, published in 1967 and 1969.
This was " the last great work to provide a synthetic account of the philosophes and their world," said Margaret Jacob, a professor of history at UCLA. "It was canonical. He just had an encyclopaedic grasp of the subject."
A long-standing interest in Sigmund Freud's ideas led Gay to train at the Western New England Institute for Psychoanalysis and motivated him to write a revisionist psychohistory of the Victorian middle classes, The Bourgeois Experience: Victoria to Freud, whose five volumes were published in the 1980s.
He also wrote the highly acclaimed Sigmund Freud: A Life for Our Time (1988), the first substantial Freud biography since the three-volume one by Ernest Jones from the 1950s.
Freud and Gay were assimilated, nonreligious Jews both nourished by and trapped in a German culture whose anti-Semitic undercurrents gathered strength around them. Their shared predicament provoked some of Gay's most personal and anguished historical writing, notably the essays in Freud, Jews and Other Germans (1978) and the autobiographical My German Question: Growing Up in Nazi Berlin (1998). Robust atheism Peter Joachim Fröhlich was born in 1923 in Berlin, where his father helped run a successful glassware business. An only child, quiet and studious, he subscribed to his parents' robust atheism and regarded himself as Jewish only by Nazi definition. "Jewish awareness? Jewish identity? These were empty slogans to them – and hence to me," he wrote in My German Question.
In 1938, Gay was forced out of his school, and his father's gentile partner appropriated the business. The next year, the family emigrated to the United States via Cuba. Because Americans found his last name difficult to pronounce, Gay changed it to its English equivalent (fröhlich means happy in German).
After graduating from the University of Denver in 1946, he entered Columbia University, where he earned a master's and a PhD, then teaching at Columbia before moving to Yale in 1969.
Affable and courtly, he spoke with the barest trace of an indefinable accent. Friends found him warm and generous. On the attack, however, he could be formidable. “He had a tough hide,” said Robert Weil, his editor at WW Norton. “He could engage in academic debate with a ferocity that was most impressive.”
In 1959 he married Ruth Slotkin, who died in 2006. Besides his stepdaughter Elizabeth, he is survived by two other stepdaughters, Sarah Glazer Khedouri and Sophie Glazer, and seven step-grandchildren.