Complex sentence: Roman Catholic Dialogue began in July, 1964 as an outgrowth of the Second Vatican Council and the new openness of the Roman Catholic Church to dialogue with other Christian denominations and other religions.
Split into simpler sentences: Roman Catholic Dialogue are a series of discussions which began during July 1964 as an outgrowth of the Second Vatican Council. These gatherings reflect the new openness of the Roman Catholic Church to dialogue with other Christian denominations as well as other religions.