[The Church] was not intended by Our Lord to be static or remain in perpetual childhood; but to be a living organism (likened to a plant), which develops and changes in externals by the interaction of its bequeathed divine life and history- the particular circumstances of the world into which it is set. There is no resemblance between the 'mustard-seed' and the full-grown tree. For those living in the days of its branching growth the Tree is the thing, for the history of a living thing is part of its life, and the history of a divine thing is sacred. The wise may know that it began with a seed, but it is vain to try and dig it up, for it no longer exists, and the virtue and powers that it had now reside in the Tree. very good: but in husbandry the authorities, the keepers of the Tree, must look after it, according to such wisdom as they possess, prune it, remove cankers, rid it of parasites, and so forth. (With trepidation, knowing how little their knowledge of growth is!) But they will certainly do harm, if they are obsessed with the desire of going back to the seed or even to the first youth of the plant when it was (as they imagine) pretty and unafflicted by evils.

-Letters of J.R.R. Tolkien, Letter 306