Subtitled, "the new humanity church for today and tomorrow", the central thesis of this book is that God intends for the church to display his glory through the unity in diversity of its members, and that therefore local churches should be actively seeking to promote diversity.

Bruce Milne begins his case by reminding us that already there is a great "worship wave" made up of people from all kinds of diverse cultures and backgrounds as each Sunday, Christians from every part of the planet meet together for worship. But he is not content for this staggering diversity to remain true only of the universal church – it must also be demonstrated in the local church.  He argues that if we can create a "new humanity" church, uniting people of all backgrounds, then this will have tremendous missional attractiveness.

The assertion of this book is that all Christian congregations, everywhere, are called to be … bridging-places, centres of reconciliation, where all the major diversities which separate human beings are overcome through the supernatural presence of the Holy Spirit.

It becomes apparent early on that this is not some kind of "politically correct" manifesto, but that Milne wants to root his message in Scripture. Racial diversity is a key theme in the book, but he sees many other diversities as equally important. He is careful to point out that it is not an unprincipled diversity though – we don’t blindly accept unbiblical doctrine or behaviour just in the name of "diversity".

In the early parts of the book, he sets out to make a solid biblical case for the importance of diversity within our local churches, and emphasises that this is a doctrine whose "time has come" as we live in increasingly culturally diverse communities. Churches therefore need to self-consciously set out to reflect the diversities of their surrounding communities.

… the calling of every local church, everywhere, if it is to be faithful to its New Testament roots, is, among other things, to be a community of reconciliation in which all the primary divisions and polarities of its surrounding culture are confronted and find resolution under the gracious reign of the Lord Jesus Christ.

He shows from the example of Jesus’ welcoming of women, children, and Gentiles that his intention was to create a new humanity that embraced those marginalised or considered disreputable. The Pentecost event shows the Spirit bridging racial,  gender and generational diversity.

We have no mandate to gather Christian communities, claiming Jesus’ name, that are surrounded by walls of exclusivity, whether or race, colour or ethnicity, gender, age or generation, social or economic status, mental and physical well-being; or communities entirely confined to those who come with impeccable histories of moral and spiritual propriety.

He warns against not just racial prejudices but cultural and class prejudices. "To reject a fellow believer is to reject Christ." The principle of diversity in unity is not simply a nice idea, but is a reflection of the very nature of the Triune God who is diversity in unity.

A few of chapters deal with some of the practical implications of building diverse churches, which are scattered with stories from his own culturally diverse church in Canada.

He is strongly critical of mono-cultural churches, and advocates involving a wide diversity of people within the worship service. Even when there are immigrant communities who do not speak the local language well, he encourages making a concerted effort to include and help them so that all can join together for worship. He even insists that where small groups structures are used, these too should be stratified, and also encourages a greater use of one-to-one discipleship, especially of new converts.

Sociologists claim that homogenous groups are stronger than diverse ones, and therefore are able to grow better, but Milne says that despite this, it is essential that we adopt a biblical rather than a pragmatic model. Ultimately, the only way we can make this succeed is if we can love one another with "grace-love" (agape), which itself requires a supernatural work of God and a death to ourselves.

As far as Milne is concerned, diversity is not optional for the local church. He ends the book with a stunning "dream" of a church that is a loving and accepting community made up of people from all kinds of diverse backgrounds. There is no denying that such a community would bring great glory to God, but it is hard work, and it is perhaps too easy for us to settle for the somewhat easier option of building church out of "people like me".

This book comes as a timely prophetic call to the church to be intentional about welcoming into the church all kinds of people. It provides theological foundations with very practical and down-to-earth application, and most of all builds faith and stirs a vision for the local church as the place people look to for unity amidst diversity in their local context.