In our own case here and now, we are actually failing to understand each other fully because I can't show you actual videotapes of what I'm talking about.
What do you mean by "fully" ? I believe I understand you well enough for all practical purposes. I don't agree with you, but agreement and understanding are two different things.
First, I don't contest the existence of verbal labels that merely refer -- or even just register as being invoked without refering at all.
I'm not sure what you mean by "merely refer", but keep in mind that we humans are able to communicate concepts which have no physical analogues that would be immediately accessible to our senses. For example, we can talk about things like "O(N)", or "ribosome", or "a^n +b^n = c^n". We can also talk about entirely imaginary worlds, such as f.ex. the world where Mario, the turtle-crushing plumber, lives. And we can do this without having any "physical context" for the interaction, too.
All that is beside the point, however. In the rest of your post, you bring up a lot of evidence in support of your model of human development. That's great, but your original claim was that any type of intelligence at all will require a physical body in order to develop; and nothing you've said so far is relevant to this claim. True, human intelligence is the only kind we know of so far, but then, at one point birds and insects were the only self-propelled flyers in existence -- and that's not the case anymore.
Furthermore, your also claimed that no simulation, no matter how realistic, will serve to replace the physical world for the purposes of human development, and I'm still not convinced that this is true, either. As I'd said before, we humans do not have perfect senses; if physical coordinates of real objects were snapped to a 0.01mm grid, no human child would ever notice. And in fact, there are plenty of humans who grow up and develop language just fine without the ability to see colors, or to move some of their limbs in order to point at things.
Just to drive the point home: even if I granted all of your arguments regarding humans, you would still need to demonstrate that human intelligence is the only possible kind of intelligence; that growing up in a human body is the only possible way to develop human intelligence; and that no simulation could in principle suffice, and the body must be physical. These are all very strong claims, and so far you have provided no evidence for any of them.
Let me refer you to Computation and Human Experience, by Philip E. Agre, and to Understanding Computers and Cognition, by Terry Winograd and Fernando Flores.
A few notes about the site mechanics
A few notes about the community
If English is not your first language, don't let that make you afraid to post or comment. You can get English help on Discussion- or Main-level posts by sending a PM to one of the following users (use the "send message" link on the upper right of their user page). Either put the text of the post in the PM, or just say that you'd like English help and you'll get a response with an email address.
* Normal_Anomaly
* Randaly
* shokwave
* Barry Cotter
A note for theists: you will find the Less Wrong community to be predominantly atheist, though not completely so, and most of us are genuinely respectful of religious people who keep the usual community norms. It's worth saying that we might think religion is off-topic in some places where you think it's on-topic, so be thoughtful about where and how you start explicitly talking about it; some of us are happy to talk about religion, some of us aren't interested. Bear in mind that many of us really, truly have given full consideration to theistic claims and found them to be false, so starting with the most common arguments is pretty likely just to annoy people. Anyhow, it's absolutely OK to mention that you're religious in your welcome post and to invite a discussion there.
A list of some posts that are pretty awesome
I recommend the major sequences to everybody, but I realize how daunting they look at first. So for purposes of immediate gratification, the following posts are particularly interesting/illuminating/provocative and don't require any previous reading:
More suggestions are welcome! Or just check out the top-rated posts from the history of Less Wrong. Most posts at +50 or more are well worth your time.
Welcome to Less Wrong, and we look forward to hearing from you throughout the site!
Once a post gets over 500 comments, the site stops showing them all by default. If this post has 500 comments and you have 20 karma, please do start the next welcome post; a new post is a good perennial way to encourage newcomers and lurkers to introduce themselves. (Step-by-step, foolproof instructions here; takes <180seconds.)
If there's anything I should add or update on this post (especially broken links), please send me a private message—I may not notice a comment on the post.
Finally, a big thank you to everyone that helped write this post via its predecessors!