He was an amateur archaeologist and organized expeditions from Rome to Mount Athos, to Syria, and Asia Minor,[3] from which he gained an interest in the early history of the Roman Catholic Church.

He then taught at the École Pratique des Hautes Études, where he influenced Alfred Firmin Loisy, a founder of the movement of Modernism, which was formally condemned under Pope Pius X.

He gained fame as a demythologizing critical historian of the popular, pious lives of saints produced by Second Empire publishers.

As editor of the Bulletin critique du littérature, d'histoire et de théologie, Duchesne kept up with current intellectual developments.

The London The Tablet said,By his rigid application of scientific methods of research and judgment, by his caustic tongue and pen, Mgr.