I have been very busy lately, with the masses of stuff I'm trying to cram into my head. Formalisms quantum mechanics and principles of thermodynamics and methods of solution of partial differential equations are all buzzing around, needing to be learned before I write tests and just because they're useful.
Then I move to reading for my project and there are all sorts of more specialised things I need to know - everything buzzing around my head is not very much at all.
Marking first year undergrad work reminds me of how much I do know, though. More than the owners of the scripts now covered in red ink (at least when it comes to physics - there are other spheres of knowledge, I know). But the difference between what we know is so very very much less than the masses of things we don't (even just in the realm of physics). None of us know very much at all.
There's a continual tension between ignorance and opportunity. We would never have the joy and excitement of discovery if we knew everything - but there's enough we don't know to go on discovering as long as we care. On the other hand, ignorance in its own right doesn't seem awfully lovely. Somehow, though, I need to love my ignorance at least inasmuch as it gives me the opportunity to abolish it. It's an odd kind of not-quite-dichotomy.