The first encyclical of Pope Leo XIV, on the social doctrine of the Church in the time of artificial intelligence, given at Saint Peter's in the second year of his pontificate. Its introduction sets the choice before this generation between building a new Tower of Babel and building the city where God and humanity dwell together. Five chapters follow: a dynamic approach faithful to the Gospel, tracing social doctrine from Leo XIII to the present; the foundations and principles of social doctrine, including the common good, subsidiarity, solidarity and integral human development; technology and dominance in the light of the promises of AI; the safeguarding of truth, work and freedom; and the culture of power set against the civilisation of love.