But you are a chosen race, a royal priesthood, a holy nation, a people for God's own possession, that you may show forth the excellencies of him who called you out of darkness into his marvelous light:

 The point is clear. So long as a brick lies by itself it is useless; it becomes of use only when it is incorporated into a building. So it is with the individual Christian. To realize his destiny he must not remain alone, but must be built into the fabric of the Church. 