The church lies at the centre of God's purpose. Christ gave himself 'to purify for himself a people that are his own'. But when we think about church, there's the tension between the ideal and the reality. The former is beautiful: God's special treasure, the covenant community, a haven of love and peace. The latter? A motley rabble needing constant rebuke and exhortation. Here we focus on the ideal, on what God intends his church to be, while all the time keeping in view the reality, so that we can grasp the changes that need to be made.