Use the passage from Gregory I's Letter to Abbot Mellitus on the conversion of the people of England to Christianity to answer the following question: Further, since it has been their custom to slaughter oxen in sacrifice, they should receive some solemnity in exchange. Let them therefore, on the day of the dedication of their churches, or on the feast of the martyrs whose relics are preserved in them, build themselves huts around their one-time temples and celebrate the occasion with religious feasting. They will sacrifice and eat the animals not any more as an offering to the devil, but for the glory of God to whom, as the giver of all things, they will give thanks for having been satiated. Thus, if they are not deprived of all exterior joys, they will more easily taste the interior ones. For surely it is impossible to efface all at once everything from their strong minds, just as, when one wishes to reach the top of a mountain, he must climb by stages and step by step, not by leaps and bounds...

What does this passage indicate the church is willing to accept in order to unify Europe under a single faith?