The newly-enthroned Archbishop of Canterbury warned of the dangers of abandoning more than 1,000 years of Christianity as he made his first sermon as head of the Church of England.
The Most Rev Justin Welby said advances such as the abolition of slavery, improvements in working conditions in the 19th Century and the creation of the NHS had been established as a result of "Christ-liberated courage".
He told the 2,000-strong congregation, "We now need further courage to tackle environment, economy, global poverty and human development".
"Today we may properly differ on the degrees of state and private responsibility in a healthy society," the Archbishop said. "But if we sever our roots in Christ we abandon the stability which enables good decision-making".
"There can be no final justice, or security, or love, or hope in our society if it is not finally based on rootedness in Christ," he added.
He told Penny Marshall before his enthronement that although he was "conscious of the responsibility" of his new position, he was "much more conscious of the love and the power of God to overcome even my failures and weaknesses":
Despite the formal tone of his sermon, Welby began by joking, "It's got a good reverberation this cathedral".
The Archbishop's enthronement ceremony marked the formal start of his public ministry as leader of the 77-million strong Anglican Communion as well as head of the Church of England.
The colourful ceremony featured Punjabi music, African dancers singing the hymn "Gbeh Kpa Kpa Ba" - or "A New Beginning" - and an organ improvisation.
For the first time in history, a female cleric - the Venerable Sheila Watson, Archdeacon of Canterbury - was given the central role of formally enthroning Welby on the diocesan throne in the cathedral, symbolising his appointment as Archbishop of Canterbury.