45 In the first place, with regard to studies, We will and ordain that scholastic philosophy be made the basis of the sacred sciences. It goes without saying that if anything is met with among the scholastic doctors which may be regarded as an excess of subtlety, or which is altogether destitute of probability, We have no desire whatever to propose it for the imitation of present generations (Leo XIII. Enc. Aeterni Patris ). And let it be clearly understood above all things that the scholastic philosophy We prescribe is that which the Angelic Doctor has bequeathed to us, and We, therefore, declare that all the ordinances of Our Predecessor on this subject continue fully in force, and, as far as may be necessary, We do decree anew, and confirm, and ordain that they be by all strictly observed. In seminaries where they may have been neglected let the Bishops impose them and require their observance, and let this apply also to the Superiors of religious institutions. Further let Professors remember that they cannot set St. Thomas aside, especially in metaphysical questions, without grave detriment.
Source: Pascendi Dominici Gregis (Vatican.va)