47 With regard to profane studies suffice it to recall here what Our Predecessor has admirably said: Apply yourselves energetically to the study of natural sciences: the brilliant discoveries and the bold and useful applications of them made in our times which have won such applause by our contemporaries will be an object of perpetual praise for those that come after us (Leo XIII. Alloc ., March 7, 1880). But this do without interfering with sacred studies, as Our Predecessor in these most grave words prescribed: If you carefully search for the cause of those errors you will find that it lies in the fact that in these days when the natural sciences absorb so much study, the more severe and lofty studies have been proportionately neglected - some of them have almost passed into oblivion, some of them are pursued in a half-hearted or superficial way, and, sad to say, now that they are fallen from their old estate, they have been dis figured by perverse doctrines and monstrous errors (loco cit.). We ordain, therefore, that the study of natural science in the seminaries be carried on under this law.
Source: Pascendi Dominici Gregis (Vatican.va)