Describing oneself as "self-taught" in a particular field is fairly common but it's actually a difficult notion to define.
I might be tempted to say I'm self-taught in music theory or general relativity but not, say, linguistics or calculus.
This is (many would say) because I studied calculus and linguistics at University but not general relativity or music theory.
But thinking about this further makes things less clear.
The only music theory I did at school was in primary school and my first year of high school where it was compulsory.
When I was in my final year of high-school, though, I sat the music exam to leave open the option for me to do a music degree at University.
I didn't actually attend any music classes, though, I just read books on my own so I think by most people's definition, I got to that level through self-learning.
Similarly with general relativity, I "taught myself" by reading advanced undergraduate and early graduate textbooks. I doubt many people would say that isn't being self taught.
I've since watched numerous videos on YouTube. Does that stop it being self-learning? Again I doubt many people would say so.
Imagine I'd worked through the videos on MIT's Open Courseware, rather than on YouTube. Say I watched the lectures that an MIT student would when learning general relativity.
Would you say I was self-taught but the MIT students weren't?
What if in addition to watching the videos, I did some of the assignments provided by MIT OCW. Would that disqualify me from claiming to be self-taught?
Presumably most people would still say that what I was doing was self-learning.
But now say I did a MOOC.
For MITx's 7.00X: Introduction to Biology, I watched Eric Lander lecture first year MIT students and I did weekly assignments and an exam. Does that mean I'm self-taught in introductory molecular biology and genetics?
If not, what was it I did that was different from the OCW case, or the YouTube-watching case, or the textbook-reading case?
But if so, if it was self-learning, what did I do differently from the actual MIT students in the class?
I'm currently doing a postgraduate diploma in Classical Greek by distance education.
In my first year, which I recently completed and passed, I read a text book, did weekly assignments and an exam each semester.
So unlike the 7.00X MOOC, I had a text book but no videos. And the weekly assignments and exams were written and marked by a human rather than done on a computer and marked automatically.
It would seem odd to say doing an actual postgraduate diploma at a University is being "self-taught" but it's also hard to see how my Greek postgraduate course is that much different from a MOOC. Or working through an OCW course. Or even just reading a textbook.
If I got a human to mark exercises I did from a general relativity textbook, would that be the magic step that changed me from being self-taught in general relativity to not being self-taught?
What if it was a test online? Or there were just answers in the back I could check myself?
Or is the notion of autodidacticism just too much of a slippery slope to really make much sense?
It occurs to me one aspect not discussed here, which might turn out to be the crucial one is the existence (or non-existence) of a schedule.
In other words, the difference between, say, reading a textbook / doing the exercises and doing a course at University with weekly assignments is the latter has a rigid structure.
In that respect "self-paced" or "self-structured" seems a lot more meaningful than "self-taught" as concepts.