One of the standard objections to the Christian message, as we saw, goes like this: how can you say the kingdom of heaven has arrived on earth, when it's obvious, looking around you, that nothing of the kind has happened? Things are still pretty bleak. Often Jesus' followers seem to be part of the problem, not part of the solution.
Jesus' own explanation of how the kingdom works is still the classic answer to this question. What did you expect: that God would send in the tanks like a totalitarian dictator, crush the opposition and set up a 'kingdom' which would leave half the world bruised and resentful? What sort of a 'god' would that be? No! God will bring in his kingdom by the same means, the same strange process, that he seems to use in the natural world. Seeds will be sown; many will apparently be lost, but others will be powerfully fruitful. ...the kingdom has indeed been launched; yes, it is making its way in the world; but no, it isn't doing so in the way you might have imagined. It is doing so in the way God has imagined: by the Sower himself becoming the seed sown in good soil, and rising again to celebrate the harvest of God's new creation.
-- N.T. Wright, Matthew 13
