Life together under the Word will remain sound and healthy only where it does not form itself into a movement, an order, a society... but rather where it understands itself as being a part of the one, holy, catholic, Christian Church, where it shares actively and passively in the sufferings and struggles of the whole Church. Every principle of selection, every separation connected with it that is not necessitated quite objectively by common work, local conditions, or family connections is of the greatest danger to a Christian community. When the way of intellectual or spiritual selection is taken, the human element always insinuates itself and robs the fellowship of its spiritual power and its effectiveness for the Church, and drives it into sectarianism.
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Dietrich Bonhoeffer [1906-1945), from Life Together [1954].