Thirty-three years ago, on September 6, 1981, Father Józef Tischner preached one of the great sermons of the 20th century at a Mass opening the second day of the inaugural Solidarity Congress in Gdań​sk. Tischner, an old friend of John Paul II and the pope’s fellow philosopher, combined the rugged good humor and patriotism of a Polish highlander with a first-class intellect. So he began his sermon with some essential truth-telling to the men and women about to deliberate the future of the Communist world’s first independent, self-governing trade union. Father Tischner didn’t tell the thousands assembled in Gdansk that...