Perception is a funny thing, isn't it? It changes all the time, depending on whom you're talking to and where you're standing.
In other words, it's subjective – the way you see the world, from your own perspective and coloured by your own values and beliefs.
One thing is for sure: it's not about objective fact, certain and established. Yet, in the skewed, logic-deficient twilight zone that is Northern Ireland, where the mouth is regularly engaged before the brain, it seems that perception counts just as much as cold, hard fact. And sometimes even more so.
That's why we had Peter Robinson refusing to back down over his remarks about "the perceived inequality of policing and judicial actions as they relate to the unionist community" and "genuine perceptions within unionism about inequalities".
The First Minister, in the customary tones of aggrieved self-righteousness that he adopts when challenged, insists that it is his duty to address such perceptions: "I am elected by the people to work on behalf of the people and to speak out when I see injustice and to act where I see need."
Did you spot the sleight-of-hand (or should that be sleight-of-mouth) at the end of that statement? Mr Robinson talks about speaking out when he sees injustice, but he leaves out the vital word – the one that makes all the difference: perceived.
Perceived injustice. By leaving out that important little word, he elevates a perception – that loyalists are being treated unfairly by the courts – to the level of truth: that loyalists are, indeed, suffering an injustice.
In the hot and shouty maelstrom of competing beliefs that defines Ulster politics, such elisions and conflations are common.
All too often, reason is kicked to one side and tribal emotion, surging through the veins of the body-politic like a Class A drug, takes the lead.
Where are the philosophers when we need them? The closest thing we have to a public intellectual is May McFettridge.
So are loyalists really getting the rough end of the judicial, or policing, stick? There have been many statistics flying about both in support of that view and against it.
SDLP policing spokesman Conall McDevitt eagerly brandished the PSNI figures showing that, while 147 people were charged with participating in an un-notified parade over the past three years, only three loyalists were charged for the same offence during that timeframe.
Peter Robinson said that, while hundreds of cases have been completed by the Historical Enquiries Team (HET), "only loyalists have been charged and the overwhelming numbers of cases completed are against loyalists".
But a PSNI statement, released to BBC Radio Ulster's Nolan Show, said that "of the 39 cases so far passed by the Historical Enquiries Team to the PSNI for further investigation, 26 relate to IRA, or INLA, murders and 13 to loyalist murders."
Of course, these are only the cases that have been referred to the PSNI by the HET – not the total number of cases the HET has investigated. All of which goes to show that the situation is complex and the statistics are open to interpretation.
But, so far, there is no clear evidence for the perception that loyalists, as a category, have been treated unfairly.
And that's the great thing about perceptions: if they're 'genuine' enough, if people believe them hard enough, miraculously they attain the same status as reality.
Again, it's all about the feeling. If I feel sufficiently strongly that I, or my community, is being discriminated against, then it follows that we surely must be.
This is how the asinine, ideologically-driven (il)logic goes and some of our politicians are only too keen to pick up the stupid baton and run with it.
That's why I was so surprised when Sinn Fein, which has rarely let the facts stand in the way of staunch adherence to its own set of ideological precepts, decided to do the decent thing and oppose the ill-judged DUP/SDLP attempt to prevent abortions outside the NHS.
Whatever its motivations, Sinn Fein deserves credit for this. For once, it has chosen to address the difficult, inconvenient facts of the matter – that women with crisis pregnancies will need abortions and the earlier the better – rather than try to twist those facts around to suit their own ends.
Perception is not reality. Or, rather, it may be your reality, but that doesn't mean it's mine.
And it certainly doesn't mean it's the truth.