By the time we're adults we're amazingly skilled at faking it - in displaying not our real selves but the selves we want other people to see. The competent mum or dad, the chatty socialite, the reassuring friend, the diligent employee. Some pretty astute detective skills are needed to cut through all the pretence and dig out the real person hiding underneath.
We don't want other people to see the secret reservoirs of malice, jealousy, violence, greed, sloth, contempt and all the other 101 varieties of untamed nastiness. And worse than that, the fleeting desire for sheer unmitigated madness - the wish to strangle our argumentative spouse, drown our impossible children, burn down the stingy bank, bomb that hideous new office block.
If we know someone really well, we'll have seen a few of these squalid impulses in unguarded moments. But it's unlikely we've seen them all, or seen them in their full naked ferocity. And the really shocking traits may be concealed so rigorously that we never discover them at all.
How many times have we read of a woman whose husband of twenty years suddenly turns out to be a serial killer, a multi-million pound fraudster, a polygamist, or a drug trafficker? They swear they had no idea what was going on, that he was an affectionate, charming husband who aroused no suspicions whatever.
Extreme emotions and beliefs are especially hard to fathom. Strange obsessions and passions and hatreds that make no sense. What fuels such vicious hostility towards a former lover? What fires such devotion to an obscure religious sect? There's something going on there we just aren't privy to.
At the end of the day there's only so much you can learn about another person. Only they can know the whole story. Only they can know exactly how they think and feel and react. Only they can know their every sordid nook and cranny. They'll always leave us guessing more often than not.
PS: Next post - three adorable little kittens called Fluffy, Taffy and Tiddles.
