The Earth is getting hotter and life as we know it is under threat. Will just a few of us survive? Or can we act together to avert the crisis?

The root cause of this looming existential crisis is our addiction to consumption of material goods, and our unquestioning acceptance of the outrageous maldistribution of wealth among individuals and nations. Can we throw off these addictions and assumptions, to tread more lightly on the Earth?

McCarthy believes that we can. He starts by delving into the last two thousand years of Christian history. He traces the role of Jesus' revolutionary teaching in a series of dramatic convulsions of human consciousness that have, suddenly and unexpectedly, changed attitudes and behaviour in previously unthinkable ways. In a world where violence, slavery, power and patriarchy were once universal, we are on the way to one that strives for peace, freedom, human rights, universal democracy, and equality for everyone.

These transformations–still in progress–are instances of a complete change of heart and mind: 'metanoia'. They are the quiet, usually unacknowledged, 'slow work of God'.

We must hope and strive for a new metanoia–one that overturns our materialist obsessions. In the final chapters, McCarthy proposes a radical way to launch this seismic change of heart, prevent catastrophe and 'save humanity from itself'.

His book is full of hope and promise. We just have to make it happen.