The Scottish Catholic moral philosopher Alasdair MacIntyre died on 21 May, at the age of 96, in South Bend, Indiana. I believe MacIntyre was the most important moral philosopher of his lifetime. He wrote books that will be read for decades, if not centuries. And he had a profound and persistent impact on the development of Catholic philosophy and theology. It is no exaggeration to say that MacIntyre changed the course of moral and political philosophy in the 20th and 21st centuries—and all for the good. Even Catholics who have never heard of MacIntyre have been affected by his work through his influence on the education of generations of priests and moral theologians.