Why do we trust our instincts when we are often proved wrong?

We probably have too much faith in our ability to assess things clearly. If you ask a sibling to give their account of any memorable occurrence in your shared childhood – the time one of you smashed the living room window with a haphazardly thrown sliotar, or when you were scuffling and destroyed a parent’s treasured heirloom – their account will invariably differ from yours. Often, it will differ in material ways – you’ll disagree on whether you broke the window from inside or outside, or you’ll have opposite accounts of an enraged parent’s response.

We are also often very bad at first impressions. You might take an instant dislike to someone only to have to admit later that you were utterly wrong. Or you might feel inclined to trust someone who has a pleasing manner, only to discover that they are a scurrilous git once you know them better. In these sorts of instances, however, we don't necessarily learn to be more open-minded next time, and we usually still insist that our sibling's account of that childhood incident is entirely wrong – "No. I remember perfectly well. First I dropped the apple tart on Granny and then the cat attacked her. It definitely wasn't the other way around!"

We are proved wrong almost constantly, but still tend to trust our instincts, our first impressions, and our senses. We are patient with children, but sceptical of them. I once had an interesting conversation with a six-year-old who insisted that she had a pet “horsepig” called “Snouty”. Apparently Snouty was prodigiously fond of carrots and would let you sit on his back. I was rightly unconvinced. When children are small, they don’t view themselves as filters processing reality and forming conclusions. They simply believe that their impressions are a source of truth, and sometimes wander into conflating imagination with reality.

You can be incorrect, and often are, but still you will trust your judgment as though it hasn't failed you terribly a million times before.

As far as I can tell, we adults are not much different, apart from being sprinkled with a liberal garnish of arrogance. You know from those disputes about childhood memories, or the times you’ve badly misjudged another person’s character, that you’re not all that reliable a filter of reality. You can be incorrect, and often are, but still you will trust your judgment as though it hasn’t failed you terribly a million times before.

Last week, while changing a duvet cover – the most existentially tiresome of all tasks – I caught my own reflection in the mirror and, thinking it was a stranger in the room, shrieked and tripped over a pillow. This impression of danger may be more animalistic and instinctive than thinking a new acquaintance seems like a bit of a gom, but both are instances of misguidedly trusting our impressions.

We look out at the world from the operating desk behind our eyes and arrogantly presume that what we see is what there really is. We forget that, like a windscreen, our view can get mucked up by the spattered cow dung and heavy rain of moods and emotions. We dismiss grizzling children’s bad behaviour when we know they’re tired, but never question whether we are less likely to see clearly because we are tired, or have a sore foot, or are craving carbohydrates. We are often not the rational beings we pretend to be, and anyone who has come close to weeping or raging on a cold morning when they get out of the shower, only to discover that all the clean towels are in another room, will know that.

The way a stick appears to bend at an angle when you submerge it partially in water comes up often in the history of philosophy. The stick hasn’t really changed shape, and we know that, but if we went by first impressions alone, we would say it had. Scepticism isn’t simply a dusty old philosophical archaism. It’s a healthy respect for our tendency to trust ourselves, our senses and our feelings too much. The fact that we feel, or believe, or insist that something is a certain way doesn’t make it so. Scepticism puts the burden of proof on everyone to justify why they think something is true, which is precisely how we can know (thank goodness) that a horsepig doesn’t exist.