and Ph.D. in political theory at The Catholic University of America where he studied under David Walsh.

His dissertation, "A Relation between Us": Religion and the Political Thought of Edmund Burke, examined how Burke hoped religion could supplement and ground the authority of law in a modern, constitutional state in circumstances with and without the formal support of a religious establishment.

Millies's academic work focused on the relationships between history, religion, and politics, especially as they intersect in the Roman Catholic tradition.

He had written widely, drawing from authors along the full spectrum including Eric Voegelin and Edmund Burke, Thomas Merton and Joseph Bernardin.

Millies became involved in controversy in 2020 when U.S. Catholic magazine unpublished an article he had written that was critical of New York Cardinal Timothy Dolan.