In a series of clear, short chapters, Leonardo Boff unpacks the mysteries of Trinitarian faith, showing why it makes a difference to believe that God is communion rather than solitude. Instead of God as solitary ruler standing above a static universe, Christian belief in the Trinity means that at the root of everything there is movement, an eternal process of life, outward movement, and love.

Boff shows how the Holy Trinity is, among other things, the image of the perfect community and the image of the church in its ideal form: not a hierarchy of power, but a community of diverse gifts and...