German Roman Catholic theologian, originator of the theological system called Hermesianism, which attempted to demonstrate the rational necessity of Christianity. His theology was deeply influenced by the philosophical works of Immanuel Kant and J.G. Fichte.

Educated at the University of Münster, Hermes was ordained in 1799 and later became a professor of dogmatic theology there. In 1819 he was appointed professor at the University of Bonn, whence his doctrines spread throughout Germany.

Einleitung in die christkatholische Theologie (1819–29; “Introduction to the Catholic Theology”) sought to establish a rational certainty for the principal tenets of the Christian faith, such as the existence of God. His Christkatholische Dogmatik (“Catholic Dogmatics”), published posthumously in three volumes (1834–35), derived the “necessity” of the contents of Catholic faith from the imperatives of duty and conscience. While popular during his lifetime, Hermes' works were sharply opposed after his death, and his orthodoxy was questioned. His major writings were placed on the Index of Forbidden Books, and his theology was condemned by Pope Gregory XVI (1835). The censure was reaffirmed by the first Vatican Council (1869–70).