I am far, far, far from being a fan of Donald Rumsfeld. But I can still recognize that he stated an observation in a clear, unique, and quotable way.
As a Maker, as a self-taught experimentalist, as an amateur engineer, you are up against the undeniable fact that there are things you don't know. But what is worse, is that there are things you don't know you don't know.
I just ran into another one of those during a random Wikipedia crawl. Say you are working with fiberglass. The known unknown is that you are dealing with toxic chemicals. MEKP (a common resin catalyst) is not something you want on your hands. So this is something you realize you need to educate yourself about, and in the meantime treat with caution; wear goggles and gloves and have a good source of fresh air, for starters.
The unknown unknown is that there is potential chemistry to know as well. Get a little acetone into the mix (as can happen easily with us prop-makers) and you have created the conditions under which acetone peroxide can form in small amounts.
Acetone peroxide is a primary high explosive.
This is the dangerous side of hobby work, Maker experimentation, small prop building, DIY. If you are doing it right, you have a healthy respect for the limits of your own knowledge, and recognize that you need to be asking questions.
But because the world is complex, and there are complex interactions possible in even some very basic systems, you won't always know there is a question involved. You simply don't know that you are walking into something you don't know.
The limits of self-knowledge are very much on my mind right now. I just published a new Instructable. It got singled out by the editors, front-pages, and got me a three-month free membership.
Problem is, I'm pretty sure I don't know what I'm talking about. I tried to say in the Instructable that I was largely self-taught and could easily be wrong. But apparently I wrote convincingly enough, there are people who think I can instruct them.
Well...follow that particular path of self-doubt far enough and you'd decide most Instructables shouldn't exist. I have to trust, I guess, that everyone within that system understands that it is amateurs speaking to other amateurs, the blind leading the blind (if you can still say that -- actually, the few blind I've known were great navigators and I'd follow them unhesitatingly).
It still makes me want to yank down the Instructable post-haste. Instead I'm probably going to settle for going back to the drawing board////PhotoShop and cleaning up some of my diagrams so they come a little closer to actually being as accurate as I fear someone might be mistaking them as.
(In my darker moments, I also think Instructables, the electronics section at Radio Shack, indeed the body of the Maker iceberg below that tiny visible bit of people actually making things, is all about selling the illusion. That most of the kits don't get finished, most of the classes don't confer tangible benefit, most of the tools sit in a drawer unused. Heck -- I know this is true for most of what I attempt! So what makes a good article or build document is not about explaining how to do something. It is about making it look easy -- or at least easy enough, for the reader to hold and own for a few precious moments the illusion that they could do it too.)