15 We renew our condemnation of those teachings of philosophy which have merely the name, and which by striking at the very foundation of human knowledge lead logically to universal skepticism and to irreligion. We are profoundly grieved to Learn that for some years past some Catholics have felt at liberty to follow in the wake of a philosophy which under the specious pretext of freeing human reason from all preconceived ideas and from all illusions, denies it the right of affirming anything beyond its own operations, thus sacrificing to a radical subjectivism all the certainties which traditional metaphysics, consecrated by the authority of the strongest thinkers, laid down as the necessary and unshakable foundations for the demonstration of the existence of God, the spirituality and immortality of the soul, and the objective reality of the exterior world. It is to be deeply regretted that this doctrinal skepticism, of foreign importation and Protestant origin, should have been received with so much favor in a country so justly celebrated for its love of clearness of thought and expression. We know, Venerable Brothers, how far you share our well-grounded anxiety on this subject, and we reckon on you to redouble your solicitude and vigilance in shutting out this fallacious and dangerous philosophy from the teaching in your seminaries, and to honor more than ever the methods we recommended in the above-quoted Encyclical of August 4, 1879.
Source: Depuis le Jour (Vatican.va)