In these days of trouble and strife, it is a relief to finally have a way to tell the dark from the light.
This barometer has been delivered to us in the form of National Party leader Judith Collins' eyebrow.
The eyebrow, Collins tells us, can be used to determine when she is joking and when she is serious.
Further testing is underway to determine its accuracy and it turns out Collins may need to fine-tune it.
A frame-by-frame viewing of a speech in which she made three "jokes" has demonstrated no discernible eyebrow rise for the first, one eyebrow raised for the second and both eyebrows raised for the third.
The joke on which she was being interrogated this week was the third.
Up at Palmerston North, Collins had been talking about people absconding from the quarantine hotels.
She then added that nobody had escaped from prison when she was the Corrections Minister.
There was a laugh from the audience.
But others were busy fact-checking. They discovered about 25 prisoners escaped under Collins' reign as Corrections Minister. Her joke was fake!
The interrogation began. Why was it a joke, how was it a joke?
And, finally, how could the citizenry of New Zealand distinguish her jokes from her statements of fact?
It went on and on through one afternoon and the next morning.
The line in question was played over and over again, often without the first part of it, which made it clearer she was engaging in a bit of comedic licence.
She was reminding them she was Crusher, and even prisoners dared not defy her (apart from the 25 who did).
In fairness to Collins, who among us has not indulged in exaggeration to get a laugh at a story?
In fairness to the jokes' critics, it was not exactly great wit. It was not a joke so much as a dramatic effect, playing to the audience.
The next day, an actual comedian appeared at Parliament – in fact, it was one who likes to mimic Judith Collins.
It was Tom Sainsbury, who was down for the valedictory of his favourite study, Paula Bennett.
While there, he no doubt took the opportunity to study Collins' eyebrows for future reference.
He would have been left confused.
In the past, Collins' eyebrow has also been used to indicate when she was being arch, when she was being sceptical, and when she was displeased with what she was being told.
National Party MPs, for example, must surely know if Collins raises her eyebrow at one of them the best course of action is to run for the hills.
In short, Collins' eyebrow is the equivalent of those all-purpose household cleaning sprays that can be used for grease, grime and the dreaded virus.
Her eyebrow is judge, jury and executioner as well as jester.
It is Marie-Antoinette's guillotine and class clown.
Collins' first policy delivery must be a chart of her various eyebrow rises so we can interpret what each one means.
In the meantime, perhaps it is safer to work on the basis that if her eyebrow rises when she says something, it is a joke.
If it rises when somebody else says something, it is danger.
This eyebrow malarkey could of course backfire on her.
She has now effectively declared her eyebrow is the equivalent of the "laugh" signs once held up at live audiences for television talkshows, to ensure the audience knew when to laugh.
The risk is that when her eyebrow rises to express anger, or disdain for the enemy, her entire audience will now read it as a direction to start laughing instead.
Collins is not the first politician to be taken to task for her jokes. She was using it to emphasise her tough talk.
Sir John Key made an art form out of using humour to play down tense situations he was facing. He too was criticised for it.
But who really wants politicians to be dried up old humourless souls?
Nonetheless, it must have been something of a relief for Collins to be standing there facing demands to explain her jokes rather than having to explain the actions of her MPs, or the lack of costings on major policies.
Little wonder her eyebrow rose further and further as the interrogation about her joke continued.