The liturgy is, as it were, a vehicle of the Divine. Even if the tradition of the liturgy does not itself belong to the Divine Tradition which is part of the Deposit of Faith, nonetheless it is a vehicle by which that Divine Tradition is transmitted. Thus, although it is indeed something which is by nature more subject to change than the Divine Tradition of faith, nonetheless, in light of the fact that this same liturgical tradition is primarily a vehicle of that very same Divine Tradition, it ought therefore to conform itself to the nature of that Divine Tradition to the greatest extent possible. Alcuin Reid insightfully points out in his book on organic development that this is analogous to the Incarnation itself, in which the Divine Second Person of the Trinity, by nature unchangeable, took on the nature of man, who is a changeable creature. And yet the man, Jesus Christ, because He was also God, was conformed in His humanity to His Divinity to such an extent that change only occurred in those natural elements of human nature in which change is necessary. Thus, the child Jesus grew into the man; but always that same person was the unchangeable God, and the moral, intellectual, and spiritual aspects of His human nature were conformed completely and without exception to the immutable Divine Nature. Likewise, the liturgy is a kind of Incarnation, in which the immutable truths of God take form in the changeable and contingent practices of the liturgy. And yet this liturgy, because it is the vehicle of the Divine, ought to be conformed in the highest degree to the immutable nature of the Divine truths which it transmits, such that any change that occurs in its tradition ought to be natural, organic - like the growth of a lving child into a man, and yet the person all throughout remains not only the same person, but the same Divine Person. Thus, the liturgy of the Church belongs eminently to the realm of tradition. Tradition is the rule according to which the liturgy must be regulated.