8 With respect to the studies, in order that the clergy should not be strangers to the advancement of all good discipline, everything that is truly useful or good will be recognized in the new methods; every age can contribute to the knowledge of human learning. However, we desire that on this subject, great attention shall be paid to our prescriptions regarding the study of classic literature., principally philosophy, theology, and the like sciences - prescriptions which we have given in many writings, chiefly in the above-mentioned Encyclical, of which we send you an extract, together with the present. It would certainly be desirable that the young ecclesiastics should all follow the course of studies always under the shadow of the sacred institutes. However, as grave reasons sometimes render it necessary that some of them should frequent the public universities, let it not be forgotten with what and how great caution bishops should permit this.(9)
Source: Fin dal Principio (Vatican.va)