He is brilliant in the 1947 film Gentleman's Agreement as recently widowed reporter, Phil Green, who moves to New York City with his son and decides to go undercover as Phil Greenburg to explore the effects of anti-Semitism for an article. Little does he know how much of an effect his decision will have on his personal life.
While the exploration of anti-Semitism in the film is confined mainly to the upper class, the film still resonates. Interestingly, this film didn't set too well with House Un-American Activities Committee and several people involved in production of the film were placed on the Hollywood black list. Still the film was well received by critics and public alike, and went on to receive Oscars for Best Picture and Director.