The "magic ingredient" may be a bridging of intuitions: an embodied AI which you can more naturally interact with offers more intuitive metrics for progress; milestones which can be used to attract funding since they make more sense intuitively.
Obviously you can build an AGI using only lego stones. And you can build an AGI "purely" as software (i.e. with variable hardware substrates). The steelman for pursuing embodied cognition would not be "embodiment is strictly necessary to build AGIs" (boring!), but that "given humans with a goal of building an AGI, going the embodiment route may be a viable approach".
I well remember that early morning in the CS lab, the better part of a decade ago, when I stumbled -- still half asleep -- into a sideroom to turn on the lights, only to stare into the eye of Eccerobot (in an earlier incarnation), which was visiting our lab. Shudder.
I used to joke that my goal in life would be to build the successor creature, and to be judged by it (humankind and me both). To be judged and to be found unworthy in its (in this case single) eye, and to be smitten. After all, what better emotional proof to have created something of worth is there than your creation judging you to be unworthy? Take my atoms, Adambot!
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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!