94 It is then fitting that, with all fatherly solicitude, We should turn Our mind to seek out suitable remedies whereby those most detestable abuses which We have mentioned, may be removed, and everywhere marriage may again be revealed. To this end, it behooves Us, above all else, to call to mind that firmly established principle, esteemed alike in sound philosophy and sacred theology: namely, that whatever things have deviated from their right order, cannot he brought back to that original state which is in harmony with their nature except by a return to the divine plan which, as the Angelic Doctor teaches, is the exemplar of all right order.
Source: Casti Connubii (Vatican.va)