In their writings and addresses [Modernists] 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
  Pope Saint Pius X, Pascendi Dominici gregis #18, 8 September 1907