The Spirit of Modernism: How God Is Purifying His Church

Bishop Athanasius Schneider identified Modernism as the most insidious enemy of the Church's constant Tradition in his book, Credo: Compendium of the Catholic Faith.

In the text, Schneider cites the 1914 encyclical Ad Beatissimi Apostolorum by Pope Benedict XV to distinguish between specific Modernist errors and the "spirit" of Modernism. According to the encyclical, those influenced by this spirit dislike antiquity and seek novelties in religious functions, the administration of Catholic institutions, and private piety. Benedict XV described Modernism as a plague that remains hidden in various places and urged Catholics to guard against its contagion.