Chancellor Angela Merkel of Germany, recalling how the Berlin Wall’s destruction 30 years ago taught her that anything was possible, exhorted Harvard’s 2019 graduating class on Thursday to reject isolationism and nationalism, embrace the fight against climate change, see the world through others’ eyes and never “describe lies as truth and truth as lies.”

Ms. Merkel, in her 13th year as chancellor and widely regarded as the leader of Western Europe, never mentioned President Trump by name in the commencement keynote speech. But she laid out a worldview that showed her deep differences both with his administration and the forces of right-wing populism that have emerged in Europe and elsewhere. And she did so on America’s most prominent academic stage.

Speaking mostly in German with a consecutive English translation, Ms. Merkel, 64, paused more than a dozen times for applause and received three standing ovations from the graduates and guests at Harvard’s commencement in Cambridge, Mass. Earlier in the day, Harvard’s president, Lawrence Bacow, awarded Ms. Merkel an honorary doctor of laws degree.

The chancellor, who has said she will leave politics in 2021, began by telling the crowd how, as a young physicist in East Berlin during the Cold War, she walked home every day, frustrated and despondent that the wall dividing the city had limited her life. All of that changed abruptly when the wall came down in 1989.