Désiré Félicien François Joseph Mercier (21 November 1851 – 23 January 1926) was a Belgian Catholic prelate who served as Archbishop of Mechelen from 1906 until his death in 1926.

In the 1860s Croquet became a missionary to the Grand Ronde Indian Reservation in western Oregon near the Pacific coast, where his surname was anglicized to Crockett.

[3] Mercier received the clerical tonsure in 1871, and was ordained to the priesthood by Archbishop Giacomo Cattani, the nuncio to Belgium, on 4 April 1874.

His comprehensive knowledge of Thomas Aquinas earned him the newly erected chair of Thomism at Louvain's Catholic university in 1882.

[citation needed] He founded in 1894 and edited until 1906 the Revue Néoscholastique, and wrote in a scholastic manner on metaphysics, philosophy, and psychology.

[5] His reputation within his field gained the recognition of Pope Pius X, and Mercier was appointed as Archbishop of Mechelen and Primate of Belgium on 7 February 1906.

Through his influence, Mercier prevented Albin van Hoonacker's Les douze petits prophètes traduits et commentés ["The twelve minor prophets translated and annotated"] from being placed on the Index.

[10] Pope Benedict XV sent his portrait and a letter of whole-hearted support to Mercier in 1916, and at one point told him, "You saved the Church!

Mercier had to leave his diocese on 20 August of that same year to attend the funeral of the late Pius X, and participate in the following conclave to elect a new pope.

[citation needed] Returning from the conclave Mercier passed through the Port of Le Havre, where he visited wounded Belgian, French and British troops.

In the Imperial German atrocities that ensued in the Rape of Belgium, thirteen of the priests in Mercier's diocese were killed, not to mention many civilians, by Christmas 1914.

[citation needed] In Ireland, Cardinal Mercier's detention and indeed the German occupation was used to help recruitment for the British Army among Irish Catholics.

[12] Following World War I, Mercier undertook an excursion to raise funds to rebuild and stock a new library of the University of Leuven.

[16] In his final days, Mercier was visited by King Albert and Queen Elisabeth, Lord Halifax, and family members.

Mercier recognized the mathematical talent of Georges Lemaître as a young seminarian, and urged him to study Einstein's theories of relativity.