Pope Pius X
Pascendi Dominici Gregis §43
Pascendi Dominici Gregis: On the Doctrines of the Modernists
43 And here we have already some of the artifices employed by Modernists to exploit their wares. What efforts they make to win new recruits! They seize upon chairs in the seminaries and universities, and gradually make of them chairs of pestilence. From these sacred chairs they scatter, though not always openly, the seeds of their doctrines; they proclaim their teachings without disguise in congresses; they introduce them and make them the vogue in social institutions. Under their own names and under pseudonyms they publish numbers of books, newspapers, reviews, and sometimes one and the same writer adopts a variety of pseudonyms to trap the incautious reader into believing in a whole multitude of Modernist writers - in short they leave nothing untried, in action, discourses, writings, as though there were a frenzy of propaganda upon them. And the results of all this? We have to lament at the sight of many young men once full of promise and capable of rendering great services to the Church, now gone astray. And there is another sight that saddens Us too: that of so many other Catholics, who, while they certainly do not go so far as the former, have yet grown into the habit, as though they had been breathing a poisoned atmosphere, of thinking and speaking and writing with a liberty that ill becomes Catholics. They are to be found among the laity, and in the ranks of the clergy, and they are not wanting even in the last place where one might expect to meet them, in religious institutes. If they treat of biblical questions, it is upon Modernist principles; if they write history, it is to search out with curiosity and to publish openly, on the pretext of telling the whole truth and with a species of ill-concealed satisfaction, everything that looks to them like a stain in the history of the Church. Under the sway of certain a priori rules they destroy as far as they can the pious traditions of the people, and bring ridicule on certain relics highly venerable from their antiquity. They are possessed by the empty desire of being talked about, and they know they would never succeed in this were they to say only what has been always said. It may be that they have persuaded themselves that in all this they are really serving God and the Church - in reality they only offend both, less perhaps by their works themselves than by the spirit in which they write and by the encouragement they are giving to the extravagances of the Modernists.
Source: Pascendi Dominici Gregis (Vatican.va)