32 But the dominion of philosophy over history does not end here. Given that division, of which We have spoken, of the documents into two parts, the philosopher steps in again with his principle of vital immanence , and shows how everything in the history of the Church is to be explained by vital emanation . And since the cause or condition of every vital emanation whatsoever is to be found in some need, it follows that no fact can ante-date the need which produced it - historically the fact must be posterior to the need. See how the historian works on this principle. He goes over his documents again, whether they be found in the Sacred Books or elsewhere, draws up from them his list of the successive needs of the Church, whether relating to dogma or liturgy or other matters, and then he hands his list over to the critic. The critic takes in hand the documents dealing with the history of faith and distributes them, period by period, so that they correspond exactly with the lists of needs, always guided by the principle that the narration must follow the facts, as the facts follow the needs. It may at times happen that some parts of the Sacred Scriptures, such as the Epistles, themselves constitute the fact created by the need. Even so, the rule holds that the age of any document can only be determined by the age in which each need had manifested itself in the Church. Further, a distinction must be made between the beginning of a fact and its development, for what is born one day requires time for growth. Hence the critic must once more go over his documents, ranged as they are through the different ages, and divide them again into two parts, and divide them into two lots, separating those that regard the first stage of the facts from those that deal with their development, and these he must again arrange according to their periods.
Source: Pascendi Dominici Gregis (Vatican.va)