I have always wondered where the で in ~である (and ~でございます) comes from.
In the answer to the question 「です」, what is it really? Is my analysis correct?, Eiríkr Útlendi states that the で in ~である is the particle で. He also writes that in "older stages of the language, you'll find just that -- あり serves as the primary copular verb".
Concluding from this, somewhere along the way the old copula あり gained the particle で.
In an answer to the question Can the である copula be explained as で (particle) + ある (to exist), i.e. "to exist in the form of ~"?, however, Snailboat presents a view on the matter by linguist Kunio Nishiyama. If I understand correctly, Nishiyama basically refers to で as the real "to be", while the ある is only there as a "dummy" to indicate tense.
It strikes me as odd that the semantic core would be omitted back when あり on its own was used as the copula. Baring a misunderstanding on my part, doesn't it seem like these two analyses of である kind of clash with each other because of this?
I have two other questions relating to this: Why was this で (or maybe にて) added to (or reinserted into) the copula あり? Also, back when あり was used as the main copula, what was the distinction between what is today the copula ~である and the existential verb ある?