At the dawn of the 20th century Pope Pius X warned against the teachings of the theological Modernists who were already infiltrating the Church:

“… in their books you find some things which might well be expressed by a Catholic, but on the next page you find other things which might have been dictated by a rationalist. When they write history they make no mention of the divinity of Christ, but when they are in the pulpit they profess it clearly; again, when they write history they pay no heed to the Fathers and the Councils, but when they catechise the people, they cite them respectfully. In the same way they draw their distinctions between theological and pastoral exegesis and scientific and historical exegesis.

“So, too, acting on the principle that science in no way depends upon faith, when they treat of philosophy, history, criticism, feeling no horror at treading in the footsteps of Luther, they are wont to display a certain contempt for Catholic doctrines, or the Holy Fathers, for the Ecumenical Councils, for the ecclesiastical magisterium; and should they be rebuked for this, they complain that they are being deprived of their liberty.

“Lastly, guided by the theory that faith must be subject to science, they continuously and openly criticise the Church because of her sheer obstinacy in refusing to submit and accommodate her dogmas to the opinions of philosophy; while they, on their side, after having blotted out the old theology, endeavour to introduce a new theology which shall follow the vagaries of their philosophers.”

— Pope St. Pius X. Pascendi Dominici Gregis [On the Doctrine of the Modernists] #18, 1907