Babies have no sense, and I mean no sense, of danger. We have all the standard babyproofing that one would find: plugged the outlets, stowed away the pointy cornered coffee table, wrapped up the cords, stashed pillows away (which are agents of death apparently), and put all the poisonous stuff up high. Fine, I get that. He's still learning.
However, the shear lack of respect for gravity befuddles me. If I am laying on the couch, he wants to climb up on the couch. If I am holding him on the couch, he desperately (and I mean desperately) wants to climb right off. And by climb, and I mean crawl to the edge and fall on his head. Maybe he'll learn if I didn't catch him, but then again he may stop learning all together, and I'm not willing to take the chance.
I always thought that a fear of heights was programmed into us pretty well. Heck, babies don't like to lay on their backs because it makes them feel like their falling. However, to babies there is apparently bad falling (aka lying on your back in a crib) and good falling (aka actually falling). One time, he actually twisted right out of someone's arms while they were holding him... securely. We still haven't figured out how he did that, which is a bit scary by the way.
Anyway, I am really looking forward to this kid learning that falling is bad, before he makes me completely grey before I'm 30.