IF A significant number of people are not happy with how they are governed then it is inevitable that they will find ways to manifest that unhappiness. Sometimes, as in South Africa during the apartheid era, it was a majority of the population who were unhappy and deliberately excluded from the political, electoral, democratic and social structures. Sometimes, as in Northern Ireland, it was a 'minority' of the population who believed that they were regarded and treated as second-class citizens.
So what are the options when you find yourself in that position? Well, the most obvious one is dialogue - with spokesmen opening channels of communication with the government and exploring avenues for change. Failing that, it may come to a civil rights campaign involving propaganda, organisation, rallies and election campaigns. Others will try to 'internationalise' their cause, seeking support from across the world and hoping that threats of sanctions and isolation will persuade the government to adopt thoroughly democratic practices.
But what happens if all of those tactics fail? What happens if the grievances and concerns of the discontented and disenfranchised are not resolved by dialogue and peaceful protest? At what point is it right - morally as well as politically - to use violence? Or, to put it another way, at what point is a terror campaign justified?
If I had been born in South Africa in 1955, rather than in Belfast, and had been black rather than white, I'm pretty sure I would have been part of a campaign to have my voice heard, my vote registered and my majority status recognised as such.
And had every door been closed to me I suspect that I would have either actively supported or, at the very least, been tolerant of a campaign of violence to force change.
When a government ignores or sidelines any significant section of the population - irrespective of what reasoning may lie behind it - history suggests that it radicalises those people. It radicalises them to the extent that huge numbers of people who are perfectly normal and peaceable in every other way react to a terror campaign on their behalf with the argument 'every other method failed'.
That's what happened in South Africa. I don't like what Nelson Mandela did. I don't view him as a saint - I think he was a terrorist. But I also think he had no other choice available to him.
Let's not kid ourselves that South Africa is now some sort of utopia or that the levels of violence and corruption aren't rampant.
That said, the Mandela who emerged from prison was not the Mandela who went into prison. The post-prison Mandela made a huge effort to shore up stability in his 'rainbow nation' and he deserves to be remembered as a genuine seeker and maker of peace.
Could we say the same thing of, for example, Gerry Adams? He likes to portray himself as a liberator and maker of peace, yet he chose a terror campaign as his first course of action. He continued to endorse a terror campaign decades after the Stormont parliament had been removed and a whole raft of legislation on housing, employment, voting rights, equality, mandatory power-sharing and an in-built 'Irish dimension' had been introduced and implemented.
He continues to endorse a terror campaign that put Sinn Fein into government in this part of the UK, even though the supposed purpose of that terror was the ending of partition and the reunification of Ireland.
It wasn't the IRA campaign that brought political and electoral change here. It was the mobilisation of the Northern Ireland Civil Rights Association, the campaigning by the SDLP, the improving relationship between London and Dublin and the influence of successive US administrations.
Indeed, I would argue that the IRA campaign actually made it a great deal more difficult to construct a peace process because we had to wait until both the IRA and Sinn Fein realised that the terror campaign was doomed - as it always had been - to failure.
Political careers can only be judged by comparing the beginning and the end and trying to determine if the person was the source of more good than harm, more compassion than hatred.
On that basis I think Mandela deserves to be judged a success. History will be generous to him but he will also generate as much hatred as hagiography.
And what of Gerry Adams? The answer to that question is pretty straightforward - Gerry Adams is no Nelson Mandela.
And no amount of whimsical tweets and reconciliation rhetoric is going to change that fact.