How can I be sure that when I hand a $50-note over to a shopkeeper, that shopkeeper will, five seconds later, acknowledge the fact and hand back the correct amount of change?
Is it not possible that, with no third party looking on, the shopkeeper might claim that you had only paid $10 or $5?
Of course, it is.
Just as the inverse is possible - that the shopkeeper receives a $5 note from me, just to hear me claim, a moment after he has tucked it away, that it was actually $50.
But in most societies, a basic level of trust has developed between members of the society. Trust is that vital lubricant without which no exchange or activity is feasible. We know that instinctively, and we try our best therefore not to erode that trust.
And so we might argue over principles or how best to do something or which values are more important, but we, as a general rule, don't argue over basic facts such as the denomination of the note I have just handed you.
That is why I find deeply troubling what appears to be a trend in Singapore's political arena: our leaders and politicians - those we should be looking up to - are arguing not over the real questions of politics (i.e. what kind of country we want to build) but over the most basic of facts.
I use the word "trend" loosely here, since I can really only cite two incidents. I would be the first to applaud if these turn out to be isolated cases.
But the quick succession of and the stark similarities between the two spats surely give cause for concern, and I make no apology therefore for erring on the side of alarmism here by saying: Let's arrest this trend before it gets out of hand.
I am referring of course to two recent clashes between the Workers' Party and the People's Action Party-led government.
In the first instance, WP and the Government disagreed over the rates charged by the managing agent for the WP-led town council in Aljunied.
In another dispute that began last month and is still ongoing as I write, WP and the National Environment Agency waged a war of words over whether or not the other side had said that hawkers would pay for scaffolding needed to clean the high areas of a few hawker centres in Bedok.
I do not want to get into the relative merits of each side's case in either of those incidents.
Indeed, my point is that I can't. I am simply unable to. When two sides choose to argue over basic facts, I have no basis on which to comment because I wasn't there or because I am not privy to the information I need to make a reasonable assessment.
I suspect many members of the public who have tried - in vain, surely - to follow some of these arguments would have felt the same frustration.
Just as somebody who wasn't there cannot possibly say anything authoritative about whether or not you had handed over a $50-note to the shopkeeper, there are parts of these PAP-WP debates - particularly the parts that involve judging whether or not X had said Y to Z - that are inscrutable to the public.
There are two possibilities on what has led to the disputes. One, it was a pure misunderstanding between two sides which engaged each other in good faith. Two, it was not a pure misunderstanding, but that one side or both were being mischievous.
Whichever is the case, let's stop it now.
These are debates that the public can do without. These are news events that even the news hound in me is quite happy to see less of.
In the long run, more of such debates will simply wear the people down and breed deep mistrust of their politicians - to the detriment of all political parties.
It will also make it harder for cooperation between political leaders to take place and for public goods to be delivered - to the detriment of the people.
And so, it is in the interest of all sides to take these fact-centred quarrels behind closed doors, and to allow public space and newspaper columns to be dominated by issues of more import, such as: How do we narrow the income gap even as we sustain our economic competitiveness? Or, how can we maintain social harmony even as we allow free expression?
For the sake of this country and of decency, let's raise our public debates above the level of banalities and trivialities.
Let's stop it now.