Welby, a former oil company executive who had been a bishop for just over a year when he was elected to Canterbury, said in his sermon that many of Britain's social advances, from the abolition of slavery to the National Health Service, come from its Christian tradition, The Daily Telegraph reported.
"For more than 1,000 years this country has to one degree or another sought to recognize that Jesus is the son of God; by the ordering of its society, by its laws, by its sense of community," he said.
Welby's 104 predecessors include St. Augustine of Canterbury, who brought Christianity to the Saxons, St. Thomas Becket, who was martyred in the 12th century, and Thomas Cranmer, who was burnt at the stake under Queen Mary I as a Protestant. Thursday was also the 457th anniversary of Cranmer's execution.
Welby has become head of a church that appears to be in decline. While millions of people in England and Wales are nominally Anglican, the number of regular communicants has dwindled.
But Welby urged Christians to take heart.
"There can be no final justice, or security or love or hope in our society if it is not based on rootedness in Christ," he said.
"Jesus calls us over the wind and storms, heed his words and we will have the courage to build society in stability."