One of the most abused pieces of terminology in the internal Roman Catholic debates over Vatican II is the word "modernism". Originally referring to the Modernist school of theology and exegesis led by Alfred Loisy and George Tyrrell, it quickly became condemned by Rome as the "synthesis of all heresies", and as with so many other theological fads soon passed out of fashion in the wake of Vatican II, when it was supplanted by the turn back to the Fathers and the nouvelle theologie. The terminological abuse lies in the denotation of this nouvelle theologie as "modernist" by those of a traditionalist persuasion, and by extension the application of the term "modernist" to all postconciliar, post-Tridentine, and post-scholastic Catholic theology and liturgics, and all the ecclesiastical condemnations pertaining thereto.
The extension of the term "Modernist" to the nouvelle theologie may seem obvious at first. At Vatican II the Church reconciled itself with modernity, embraced modernity, and apparently embraced the anathematized proposition from the Syllabus of Errors that the Church can and must reconcile itself with modernity and progress.
The problem is that conciliar and postconciliar theology is not the successor of classical Modernism at all. Arguably, only two true successors of classical Modernism persisted in influencing Catholic thought into the conciliar era, Teilhard de Chardin and Hans Kung, and both are, frankly, unique exceptions rather than leaders of their schools, and if we follow the line of argumentation proposed here, Kung would be only dubiously a Modernist at best. Instead, the nouvelle theologie turned to a different inspiration - the theology of Protestant thinker Karl Barth. Barth was a student of the leading figure of Protestant Liberalism, Adolf von Harnack, and he was a major influence on both Rahner and von Balthasar, whose students in turn became the "Concilium" and "Communio" movements in contemporary Catholic theology.
Liberalism and Modernism are often grouped together as simply the Protestant and Catholic equivalents of each other. Such a categorization overlooks some radical differences in their philosophical underpinnings, however. Modernism was essentially immanentistic in its philosophy, depending on the dynamic ontology of the likes of Maurice Blondel, Henri Bergson, with more remote affinities to Schopenhauer. Protestant Liberalism bears direct descent from German Romanticism, with whom Friedrich Schleiermacher was affiliated. Liberalism bears the inheritance of Schelling and Hegel; Modernism that of Schopenhauer. Both owe their origin to Kant, but as any student of the history of philosophy knows, among Kant's heirs the division between the Hegelians and the partisans of Schopenhauer run deep. To conflate the two schools is irresponsible and dishonest at best.