This year is being celebrated in many countries as the 500th anniversary of the Protestant Reformation. It was in October 1517 that Martin Luther, a professor at the University of Wittenberg, nailed his 95 theses to the door of the church in Wittenberg, an event that is seen as a key moment in the Reformation.
The Reformation changed many lives with its message of personal salvation through Grace alone, by Faith alone, in Christ alone, according to the Scriptures alone, and with all the glory to God alone. It also changed the course of European, and ultimately world, history.
The 500th anniversary of such an important event has been marked around the world with books, conferences, exhibitions, church services and radio and television programmes.
Here in Belfast, the Linen Hall Library has worked with the Luther 500 initiative to develop and host an exhibition and two lectures on the Protestant Reformation, and there have been many commemorative events across Ulster.
The Reformed faith was firmly established in Ulster in the early-17th century. Scottish and English Protestants settled in Ulster as part of the official plantation, but even before that many lowland Scots had already settled in Antrim and Down.
A Reformed Church of Ireland emerged around that time, and the Scottish Presbyterian influence was especially strong. In many ways, Presbyterianism in Ulster was the eldest daughter of the 'mither kirk' in Scotland.
The Six Mile Water Revival of 1625 and the formation of the first presbytery in 1642 were key events in embedding that Scottish Reformed tradition and giving it permanence and influence.
That Protestant Reformed tradition, along with other religious traditions, helped to shape modern Ulster. It placed, for example, a strong emphasis on education, so that educated men and women would be able to read the Bible for themselves, and Christians helped to found many schools.
There is also something inherently democratic about the Presbyterian system of church government and the right of the members to elect the church elders. It had a profound influence on shaping our society, and we cannot understand the past without recognising that.
Today we live in a more secular age, but the Christian faith remains an important influence on our society, especially in Northern Ireland.
Unfortunately, we are seeing more and more attempts to silence the Christian voice and to slander our Christian heritage.
We seem to be entering what AN Wilson described as a new "dark age of intolerance", where freedom of speech is being eroded.
The twitterati of the Left are certain to target anyone espousing a Christian, or socially conservative, worldview in an effort to bully them into silence.
The same is happening more generally in the public square, with a desire on the part of the secularists to push a Christian worldview out of the public space.
At such a time, we do well to reflect on the action of Martin Luther, who refused to be silenced and took his message out of the study and the library of the university and into the very heart of public life.
Meanwhile, our Christian heritage is slandered with no recognition of the reforming zeal of Christians such as William Wilberforce, who wrote that Almighty God had set before him "two great objectives: the suppression of the slave trade and the reformation of society".
Lord Shaftesbury, another devout Christian and evangelical Protestant, sought to improve the conditions of factory workers and miners and was president of a union of schools for poor children.
We can also think of Lord Cairns, another evangelical social reformer, who was born at Cultra in Co Down and rose to become Lord Chancellor of Great Britain.
The Tolpuddle Martyrs in England, who are often regarded as the first trade unionists, were led by a Methodist local preacher, and a former general secretary of the Labour Party once said that the party owed more to Methodism than Marxism.
Of course, that was a very different Labour Party from the current Labour Party of Jeremy Corbyn.
This 500th anniversary provides an important opportunity to reflect on the Reformation, the faith of the reformers and the fruits of their labours.