In his speech to Congress, Pope Francis highlighted the contributions of four Americans he said helped shape fundamental values that will "endure forever in the spirit of the American people."
Americans are familiar with two of those cited by the pope — President Abraham Lincoln and civil rights leader Martin Luther King Jr. — but social activist Dorothy Day and writer Thomas Merton are less well known.
Day, long a revered figure among Catholic progressives, co-founded the Catholic Worker Movement in the 1930s as she sought to help the poor and homeless. A pacifist, Day was arrested many times as she fought to bring attention to the plight of the poor and working class.
Merton, a Trappist monk and poet, advocated interfaith dialogue and spoke out against the Vietnam War and nuclear weapons.
As a young woman Day had an abortion, and the pope's choice to highlight her service was seen by some observers as a demonstration of his vision of a merciful church. The pope has said he will allow priests to grant absolution for abortion, which the Catholic Church views as a grave sin.
Francis said in his speech that a nation can be considered great when it defends liberty as Lincoln did; when it fosters dreams of full rights for all, as King did; when it strives for justice for the oppressed, as Day did; and when it encourages peaceful dialogue, as Merton did.
Fr. James Martin, a Jesuit priest and author, called the pope's words "rehabilitation" for Day, who was once told by a prominent U.S. Cardinal not to call her group "Catholic."
Martin said on Twitter that Day was an "apostle of the poor" and Merton an "apostle of dialogue," adding of the pope's decision to highlight them: "Amen."
