http://www.technologyreview.com/view/514136/your-body-does-n...
> When you drive a nail with a hammer, you feel as though you are acting directly on the nail, not “asking” the hammer to do something for you. In contrast, “present at hand” describes a tool that, in use, causes you to “bump up against some aspect of its nature that makes you focus on it as an entity,” as Matt Webb of BERG writes. Most technological “interfaces”–models that represent abstract information and mediate our manipulation of it–are “present at hand” almost by definition, at least at first. As Webb notes, most of us are familiar enough with a computer mouse by now that it is more like a hammer–“ready to hand”–than an interface standing “between” us and our actions.
A mouse became “ready to hand” just like a hammer did. Have you every seen a child with a hammer or other tool? It's “present at hand” for them until they master it. So the real question is not "how is Glass different than hammer?", it's "how is Glass different than a mouse?"
> Still, a mouse is also like a hammer in that it is something separate-from-you that you can pick up and set down with your hands. What if the “mouse” wasn’t a thing at all, but rather–as in the Fjord example of “staring to select”–an integrated aspect of your embodied, phenomenal experience?
Do we really think that the thing that makes a mouse a good interface device is that it's a solid object? Look, I get the idea that if you try to overload bodily actions with new results on top of the existing ones (i.e. making thinks "selected" when you just wanted to look at them) you'll obviously get problems. But does anyone really think that, say, rubbing your fingers together would be some horrendous input method merely because it doesn't have a physical object? No, not as long as you rarely had need to rub things in real life at the same time as you were using the device.
It's a good question, but I don't think the answer is as clear as you make it out to be. Elsewhere, Pavlus has written about Brett Victor, and some of what he's saying here is an extension of Victor's ideas about interface design.
http://worrydream.com/ABriefRantOnTheFutureOfInteractionDesi...
My own view of the camera in Glass is that it's the lynchpin for a good gestural interface. But when I imagine how this would work, I instinctively prefer the idea of using a pen (or something similar) to my empty hands. Perhaps it's because I've done a lot of painting and drawing, but I actually feel that the tool makes me more expressive, not less. In other words, it brings a level of precision to gestures that unaided hands don't supply - not unlike the way a conductor uses a baton when, strictly speaking, he could get by with just his arms and hands.