I think from time to time all of us can feel invisible. When I was young I dreamt I had it as a power; I dreamt it even more frequently than the power to fly. It felt good to be able to enter a room and not have to say or do anything, to observe other people's lives and hear their conversations and feel connected with the world without the awkwardness and shameful self-exposure of having to engage with it. These are the dreams of the introverted and insecure and shy.You learn to manage that anxiety as you grow older, but invisibility lingers. Like all superpowers, what begins as a gift can start feeling like a burden. There have been times in my life when I've been convinced that I leave no footprint on the Earth nor trace in people's memories. When I leave the room, I imagine that everyone instantly forgets I was ever there. I am frequently surprised when people I've met only once or twice remember me.With time the power of invisibility becomes the curse of invisibility. People in families or with loving partners are inoculated against this, but if you are old or alone or both it can haunt you: this sense when you're in public that the world doesn't see or need you, that it does very well without you, that it hardly knows you're there.I happen to live in a neighbourhood where there are plenty of single people and old people, and when I walk the streets I sometimes sense the trills of loneliness between us: the conviction not that we are alone, since clearly there are hundreds of us out here, but that we are unseen, that we do not exist, however superficially, in anyone's else's mind.And yet.When I go walking in my neighbourhood I wear a floppy hat that can only be worn by a man who suspects he stalks the streets unseen. It lacks elegance or grace, my hat, and you would not wear it to the races but it keeps the sun off my face. This week I went up the street to do some chores. I was a little impatient, and whenever I am impatient on a walk I unfailingly find myself behind one or another older gentleman with an unsteady grasp of the flow dynamics of the pedestrian arts. He meandered down the centre of the sidewalk like Hillary Clinton, now weaving left, now right, his veerings finely calibrated to my attempts to overtake him. I kept having to fall back, gnashing my teeth.And then - at last! A crossroad! Crossroads are kryptonite to the older gentlemen! He came to a knobbly halt and with a spurt I slid past on the inside and was clear. Hoorah!Six or seven blocks up the road I conducted some uninteresting business involving the return of a bathroom scale. "It's broken!" I said humorously to the manager. "It keeps registering my weight consistently five kilograms too high! Sometimes five-and-a-half!"A little later I was busy in another part of the centre, poking an avocado and wondering how it could cost R35 - is there a Kinder Surprise in the middle? Is it carved from purest malachite? - when a voice behind me said, "Weren't you wearing a hat?"I wheeled. It was the older gentleman. "Didn't I see you on the street just now," he said, "wearing a hat?"I clutched at my head. It was true! I must have left it behind when I was engaging in witty repartee over the bathroom scale. I thanked him and flew back up the escalators and retrieved my precious headgear. ("So the story has an unhappy ending," said my wife, when I related it that night and assured her I still have my hat.)On my way out I went back to the grocery store and found the elder gentleman. He hadn't moved that far. I thanked him, and he started telling me about how pricey it is to replace a mop, but he needs a mop, because his mop is broken. I considered telling him about the avos but I didn't want to get drawn into a conversation so I backed away, thanking him again, thanking him a third time and escaped out into the street.And so I walked along thinking about how he had recognised me, a stranger from the street, and how we're not as invisible to each other as we sometimes feel, and it was only when I arrived home that it occurred to me how little it might have cost me to tut a little with him about the price of mops and avocados. It occurred to me that being seen doesn't mean much at all unless we see people back...