How odd, the difference:

You are walking on a city block, neither empty nor particularly crowded. It is early morning, and walking towards you, you see someone you don’t recognize. At a certain distance, the most common occurrence will be, perhaps, a smile, should you be a woman; or a nod of some variety, if you are a man. The combinations and possibilities are too numerous to list and are immaterial, as the point to be made is that this is one of the strangest events conceivable, and yet it is so everyday that I suspect few people give it any thought at all.

How odd, indeed, the difference:

You are walking in the wilderness—there is nothing but, as the first cities will not rise for another 10,000 years—and hear something strange in the distance ahead of you. It doesn’t matter, really, in what sort of wilderness you find yourself. You and yours have quite likely lived in just such a wilderness for a dozen generations or more. That is to say, you know how to move, how to hide, and how to deal with danger. And what you hear in front of you is perhaps the most terrifying sound you will ever hear, one which signals immediate, mortal danger. It sounds like there is another person walking somwhere in front of you, and the sound is growing louder.

You are alone—something which you have been taught all your life to avoid at all costs, but who knows? Perhaps your camp, along with your entire extended family was butchered in front of you a few days prior—and you know no one else from any family or clan or tribe in the vicinity. You have, in fact, wandered into a part of the wilderness that you don’t know particularly well. What you do know, however, is that an unknown human (or something very much like one) is walking toward you.

Can you imagine, then, if this stranger were to emerge from whatever cover he or she is currently behind, continued to walk toward you, fully aware of your existence and your walking in his direction, deliberately avoiding any sort of active acknowledgement of presence, until forced to by sheer proximity, only to give you some sort of vague smile? A kind of nod? And then, to part ways forever?

I cannot imagine this, though I do every single day of my life.