Pope Saint Pius X noted that it is eminently possible for a Modernist, who has a "double mind," to be true to his Modernism part of the time while sounding like a Catholic most of the time:
The Modernists completely invert the parts, and of them may be applied the words which another of Our predecessors Gregory IX, addressed to some theologians of his time: "Some among you, puffed up like bladders with the spirit of vanity strive by profane novelties to cross the boundaries fixed by the Fathers, twisting the meaning of the sacred text...to the philosophical teaching of the rationalists, not for the profit of their hearer but to make a show of science...these men, led away by various and strange doctrines, turn the head into the tail and force the queen to serve the handmaid."
This will appear more clearly to anybody who studies the conduct of Modernists, which is in perfect harmony with their teachings. In their writings and addresses they seem not unfrequently to advocate doctrines which are contrary one to the other, so that one would be disposed to regard their attitude as double and doubtful. But this is done deliberately and advisedly, and the reason of it is to be found in their opinion as to the mutual separation of science and faith. Thus in their books one finds some things which might well be approved by a Catholic, but on turning over the page one is confronted by other things which might well 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 are dealing with history they take no account of the Fathers and the Councils, but when they catechize the people, they cite them respectfully. In the same way they draw their distinctions between exegesis which is theological and pastoral and exegesis which is scientific and historical. So, too, when they treat of philosophy, history, and criticism, acting on the principle that science in no way depends upon faith, they feel no especial horror in treading in the footsteps of Luther and are wont to display a manifold contempt for Catholic doctrines, for the Holy Fathers, for the Ecumenical Councils, for the ecclesiastical magisterium; and should they be taken to task for this, they complain that they are being deprived of their liberty. Lastly, maintaining the theory that faith must be subject to science, they continuously and openly rebuke the Church on the ground that she resolutely refuses to submit and accommodate her dogmas to the opinions of philosophy; while they, on their side, having for this purpose blotted out the old theology, endeavor to introduce a new theology which shall support the aberrations of philosophers. (Pope Saint Pius X, Pascendi Dominci Gregis, September 8, 1907.)