Joseph Ratzinger (in Credo for Today), reflecting on the gospel reading for this feast of the Immaculate Conception, writes:

Mary is identified with daughter Zion, with the bridal people of God. Everything said about the ecclesia in the Bible is true of her, and vice versa: the Church learns concretely what she is and is meant to be by looking at Mary. Mary is her mirror, the true measure of her being, because Mary is wholly within the measure of Christ and of God, is through and through his habitation. And what other reason could the ecclesia have for existing than to become a dwelling for God in the world?God does not deal with abstractions. God is a person and the Church is a person. The more each one of us becomes a person, person in the sense of a fit habitation for God, daughter Zion, the more we become one, the more we are the Church, and the more the Church is herself.