I have one such memory dating back to when I was six.
In my memory I'm standing in our garden in Kent. It's a beautiful day and I'm looking up at a brilliant blue sky. But I'm not my usual carefree, six-year-old self. The comforting certainties of my world have been rudely undermined.
Coming from out of the blue, both literally and figuratively, a realisation has shaken me to the core . . . the realisation that there's no way to prove that the blue I'm seeing above my head is the same colour being seen by everyone else.
What if my blue was my mother's green . . . or, equally disturbing, if my blue was my father's purple? There was no way of knowing.
Then, to further add to this confusion comes the discovery that my left eye and my right eye see slightly different shades of the same colour. Not even my two eyes can agree on the vexed subject of blue!
What, I wondered anxiously, of my other senses? When I was listening to music, did I hear the same notes as those around me?
When I bit on a peppermint cream, was my flavour of peppermint the same as that of my friends?
It's a long time since I was six, but the questions that bothered me then remain every bit as valid now.
Do you see the same blue as I do? Who knows!
You may be wondering what it was that re-awakened such vivid childhood memories and prompted this letter.
It was a photo that I saw recently at an exhibition. The photo was of a man . . . someone I'd never met and about whom I knew nothing. But the photo told me so much. I could recognise the authority in his eyes . . . the generosity in the lines of his mouth . . . his face conveyed a lively interest in the world around him.
I looked into the eyes of this man I didn't know and felt a sense of empathy and friendship . . . I liked this man, I knew this man.
Then, once again, I was pulled up short by a thought . . . would anyone else, on looking at this photo, see the same man that I saw? Would they interpret the same qualities?
Would their 'blue' be the same as my 'blue'?
Building on those basic queries of my childhood, am I right in concluding that the senses don't show us what's outside, instead they reveal what's inside?
If it isn't inside me, I can't recognise it.
The external world is a potent trigger, but it's the interpretative mechanism inside us that gives the outer world its colour, shape and form.
Why does some music move me so deeply? Not because of the sequence of notes, but because of the emotional body within me that resonates with the music.
Why does a sunset cause me to hold my breath? Not because of the earth's rotation on its axis, but because of an inner acknowledgement of the very existence of heart-stopping beauty.
Why do I enjoy sitting down and sharing my thoughts with you?
Now that's a question we'll have to leave for next time . . . !