Giuseppe Pecci was a Jesuit Thomist theologian whose younger brother, Vincenzo, became Pope Leo XIII and appointed him a cardinal. The Neo-Thomist revival, which Leo XIII and his brother Giuseppe, Cardinal Pecci originated in 1879, remained the leading papal philosophy until Vatican II.

Pope Leo XIII was head of the Catholic Church from 20 February 1878 until his death in July 1903. Living until the age of 93, he was the oldest pope, whose age can be validated, holding office and had the fourth-longest reign of any pope, behind those of St. Peter, Pius IX and John Paul II.