Why are these longings so important? For a Christian, these longings lead to hope. We need to long for that oneness and knowledge of God in order to hope for those same things. We need to long for a peaceful world before it can start to happen. We need to long for a perfect community of believers before we can hope for it.
However, this hope for a better community and world is empty if there is no action behind it. We need to consciously work for shalom, the ultimate peace. This is our call as Christians: to spread God's peace, God's shalom, and God's kingdom throughout our world. We have to hope that we can accomplish these things, but at the same time acknowledge that this world will never be perfect until Christ comes again.