CATHOLIC ENCYCLOPEDIA: Modernism: "THE PSYCHOLOGICAL CAUSES OF MODERNISM
Curiosity and pride are, according to the Encyclical 'Pascendi', two remote causes. Nothing is truer; but, apart from offering an explanation common to all heretical obstinacy, we ask ourselves here why this pride has taken the shape of modernism. We proceed to consider this question. In modernism we find, first of all, the echo of many tendencies of the mentality of the present generation. Inclined to doubt, and distrustful of what is affirmed, men's minds tend of their own accord to minimize the value of dogmatic definitions. Men are struck by the diversity of the religions which exist on the face of the earth."

Modernism. Know it. Eat it. Maybe even smell it. Sworn enemy of religion. Most popular philosophy in the Northeast.

This is a good introduction I think. I don't trust the Catholic Encyclopedia for serious info any more than I trust Encyclopedia Brittanica for serious info, but they're usually on the level. And I think a cursory review would be helpful to the mindsets of all.

Also recommended: The Everlasting Man, The Abolition of Man, and Fatherless America. I think they all address the subject.