One time when I was older I was led from the chamber beneath my own tunnel and along a winding dark passageway until emerging into what seemed like the outside world.
There was a sky! Or at least there seemed to be. A sky above a soft landscape of countryside greenery that stretched, or seemed to stretch to a far horizon. A deep blue sky. Almost unreal in its blueness. Ah... That gave me pause for thought.
'Is that sky real?' I asked. 'It looks a bit like a painted dome.'
'What does it matter? You will never reach it so you will never know. So what does it matter? It can be whatever you want it to be, for you.'
'But I'd like to know if it is real. I would not want to think that something is real if it isn't.'
'Why not? What does it matter, if you'll never know?'
'But I might know, some day.'
'You won't. Trust me. You won't'
'But you might tell me.'
'Ha! Always assuming that I know myself, but if I did tell you how would you know if I was telling the truth or not?'
'Hmm... I wouldn't.'
'But maybe I could investigate for myself.'
'Hah, maybe, but then how would you know that what you thought that you discovered was real or not?'
'Well if I got up there somehow and hit my hand against it and it was hard, I would know that it was not real sky.'
'Really? Have you ever got to the top of what you call real sky to try that?'
'You'll never know my lad. The most you may ever know is that something does not behave in the way you expected it to behave, like if you discover a hard sky, but you'll never know, deep down, what is real and not real and even what real, eh... what real really means.'
Yes, that really happened to me one time when I was older, beneath the tunnel.