Basically, I am somewhat confused when a quotation should be capitalized. My understanding is that if a) one quotes the full original sentence and b) this quotation is set off by a colon, semi-colon or comma one keeps the beginning of the quotation capitalized. This is my understanding from reading the Turabian and other relevant books. Is this correct?
The Turabian explains:
In most disciplines, you may change the initial letter of a quoted passage from capital to lowercase or from lowercase to capital without noting the change. If you weave the quotation into the syntax of your sentence, begin it with a lowercase letter. Otherwise, begin it with a capital letter if it begins with a complete sentence, with a lowercase letter if it does not.
The Turabian gives the following examples [labelling added to facilitate discussion]:
Original: As a result of these factors, the Mexican people were bound to benefit from the change.
[b] Fernandez claims, “The Mexican people were bound to benefit from the change.”
[c] Fernandez claims that “the Mexican people were bound to benefit from the change.”
[d] Fernandez points out that “as a result of these factors, the Mexican people were bound to benefit from the change.”
[e] “The Mexican people,” notes Fernandez, “were bound to benefit from the change.”
However, I am still not sure whether there are any other instances (particularly if the quotation is not set off by a colon, semi-colon or comma) when the beginning of a quotation is capitalized.
Moreover, I am not quite sure what "complete sentence" means in the Turabian explanation. Does it mean the complete original sentence or a grammatically intact sentence. So there is one further specific question I have:
When I do not quote the full original sentence but the quote is still a grammatically intact sentence, would I still capitalize the beginning of the quotation? In other words, is it ever the case that if the word that starts the quotation is not capitalized in the original I would still capitalize it in my writing (except, of course, if it follows a colon or semi-colon. In these cases I understand that capitalization is needed in any case)? I always though that as long as I only quote parts of the original sentence and weave it into my own sentence no capitalization is necessary.
Addendum: I should add that the original sentence the Turabian gives is for its examples is as follows: “As a result of these factors, the Mexican people were bound to benefit from the change.” Here I don't quite understand then why we should say “Fernandez claims, ‘The Mexican people were bound to benefit from the change.” "The" is not capitalized in the original, so is this capitalization optional?
P.S.: I asked a somewhat similar question here: Academia SE: When to capitalize the beginning of a quotation?