I think you’re right about how I used “that” as a connector. I intiuited that “that” was connecting “thesis” and “we can learn from our mistakes” but I couldn’t really see exactly how. I thought about it more and looked some stuff up, including my previous research on “that”. Learning Grammar - Parts of Speech Analysis and Trees - #33 by Fire
It’s making more sense to me now (after several hours of reading and thinking about it).
“That” is a relative pronoun, introducing the relative clause “that we learn from our mistakes”. Relative clauses function as adjectives so they have to be modifying some noun. I don’t think I identified the “that” clause as a relative clause so I didn’t consider what it would be modifying.
I think it would help my analyses to remember, or keep in mind, that the relative pronoun, which introduces a relative clause, is part of the relative clause. I think I sort mentally separated them when they should go together as a unit.
I also forgot that dashes increase emphasis. I read it in a grammar book that I have but it didn’t stick with me. I was implicity treating dashes basically the same as parenthesis.
My attempt at the corrected tree:
[are [and [essays [(The)]] [lectures [(The)]] [of [which [is [book [this]] [composed]]]]] [variations [upon [theme [one] [very] [simple] [-- [thesis [the] [that [learn [we] [from [mistakes [our]]] [can]]]]]]]]]
