Pope Francis has opened a gathering
of more than 200 senior Roman Catholic bishops by urging them not to impose what
he called "intolerable moral burdens" on believers.
They will be joined by lay Catholics to debate abortion, contraception, homosexuality and divorce.
The synod will last two weeks and no immediate changes are expected.
At a Mass opening the gathering, the Pope said he hoped bishops would participate freely in the discussions.
"Synod gatherings are not meant to discuss beautiful and clever ideas, or to see who is more intelligent," Pope Francis said. Rather, it's an opportunity to "work generously with authentic freedom and humble creativity," he said.
Previous synods have had set agendas, with proceedings tightly controlled by the powerful cardinals of the Roman Curia, the central government of the Church, correspondents say.
Many Catholics hope that Pope
Francis' reformist attitude will help to modernise and revitalise the
Church
Pope Francis was elected to lead the Church in 2013 after his predecessor Benedict XI retired
On Saturday, Pope Francis led crowds in the Vatican's St Peter's Square in a vigil to prepare for the Synod.
Last year, a global survey launched by Pope Francis suggested that the majority of Catholics rejected Church teaching on issues such as sex and contraception.
On Saturday, the Pontiff said he hoped Bishops would respond to the "epochal changes" that families were living through.
As one of the world's oldest religious institutions, the Catholic Church is in no hurry to change its teachings, says the BBC's religious affairs correspondent Caroline Wyatt in Rome.
Despite that, many Catholics are hoping the meetings might lead to some change, our correspondent adds.
After these two weeks of debate, the Synod will gather again in a year's time to continue its review.