The Vatican knows exactly how weak these arguments are, MacCulloch told the "Zeit" supplement "Christian and World."
Priestly marriage was the norm in the Catholic Church until well into the Middle Ages. He would tell the Vatican that his views on marriage and sexuality are a construct of the High Middle Ages and not of eternity.
Rome can quickly change its views, MacCulloch said. The Vatican has done this several times in history.
Before Vatican II, it was said that there was no salvation outside the Church – it was different afterwards. MacCulloch is Professor Emeritus of Church History at Oxford University.
His latest book, "Lower Than the Angels," was published in February.
The historian hopes that conservative readers will also discover a "subversive message" in it.
Celibacy not durable
Addressing married clergy of other denominations, MacCulloch pointed out that these can convert to Catholicism and become Catholic priests.
He estimates that around a third of Catholic clergy working in England consist of converted, married Anglican priests. "This is not tenable to those you force into celibacy," he said.
Even the argument of Pope John Paul II that the Church has no authority to ordain women as priests does not convince the historian.
It is known that there were deacons in the early church, in some places until the early Middle Ages.
“I am not impressed by these apparent obstacles of consecration, whether it be marriage, be it gender. Martin Luther wasn't either."
The central idea of the Reformation was the abolition of celibacy, according to MacCulloch.
Luther had emphasized that there should be no fundamental difference between clerics and lay people.
"He thought this was a great fraud and didn't want to live like that himself."