Traditionalism, in the context of 19th-century Catholicism, refers to a theory which held that all metaphysical, moral, and religious knowledge derives from God's revelation to man and is handed down in an unbroken chain of tradition.
[1] It denied that human reason by itself has the power to attain to any truths in these domains of knowledge.
[2] It arose, mainly in Belgium and France, as a reaction to 18th-century rationalism and can be considered an extreme form of anti-rationalism.
[1] Their doctrines were advocated in a modified form by Louis Eugène Marie Bautain, Augustin Bonnetty, Casimir Ubaghs, and the philosophers of the Louvain school.
[3] The fundamental distrust of human reason underlying traditionalism was eventually condemned in a number of papal decrees and finally ruled out by the dogmatic constitution Dei Filius during the First Vatican Council in 1870.