Belgian cardinal-archbishop of Mechelen; primate of Belgium. A Thomist scholar, he had several of his works translated into other European languages. He was known for his book, Les origines de la psychologie contemporaine (1897).  Mercier is noted for his staunch resistance to the German occupation of 1914–1918 during the Great War. After the invasion, he distributed a strong pastoral letter, Patriotism and Endurance, to be read in all his churches, urging the people to keep up their spirits. He served as a model of resistance.
 
SIG - Vintage signature (1921) clipped from a Christmas letter to Cardinal Gasquet, archivist of the Church. Only signed by Mercier Your humble and devoted servant, D.J. Card. Mercier, arch Mechelen. Accompanied by a small b/w litho print taken from a book.