Just a few weeks ago, my five-month-old son suddenly discovered that he had hands. He's been staring at them, intentionally grasping objects, waving and gesturing quite a bit since them. Thought of another way, just a month ago, any solution to any problem that required the use of hands was an "unknown unknown" to my son.

It's been amazing to watch my son as he discovers things most of us take for granted, as he changes "unknown unknowns" into "known unknowns" or even "known".