In summary, the passage is a quote that has been edited and so needs words added to make sense. There are lots of reasons for adding bits like this - usually to shortened the quote, comment, clarify, or shift blame. The Carlyle quote is so heavily edited we'd call it a "franken-quote" almost - a monster edited together from many parts. Missing parts of the quote are indicated by ellipses "..." (three dots).f
This would be correct - sections enclosed by square brackets inside a quotation are not part of the original text being quoted. There are lots of reasons for adding bits like this - usually to shorted the quote, comment, clarify, or shift blame.
n the second example, Carlyle is being quoted ... the start of the quote is "[A]ll" ... this tells you that the passage quoted is from the middle of a sentence - the actual word written was "all" but the rules of English mean it now needs a capital. Since that is not what Carlyle wrote, the cap has to be in square brackets.
Missing parts of the quote are indicated by elipses "..." (three dots). The Carlyle quote is so heavily edited we'd call it a "franken-quote" almost - a monster edited together from many parts.
This leaves "[sic]" which means "that is really how it appears in the original" - otherwise a grammar or spelling mistake in the original, and faithfully quoted, may be blamed on the author.
eg. Ryan_m_b wrote (above):
"[T]he passage is a quote that [sic] has been edited ... to make sense [of it]."
For reference, here is the original. Don't worry, it's in the public domain. If you compare the quotation to the original, you will see the meaning of the brackets and the ellipses. As Simon Bridge pointed out, [sic] refers to the fact that the word 'were', just before it, is incorrect but reported verbatim (in other words, blame Carlyle, not me). Sic is the latin word for 'so'.
Carlyle said:
They were the leaders of men, these great ones; the modellers, patterns,
and in a wide sense creators, of whatsoever the general mass of
men contrived to do or to attain; all things that we see standing
accomplished in the world are properly the outer material result, the
practical realization and embodiment, of Thoughts that dwelt in the
Great Men sent into the world: the soul of the whole world's history, it
may justly be considered, were the history of these. Too clearly it is a
topic we shall do no justice to in this place!
One comfort is, that Great Men, taken up in any way, are profitable
company. We cannot look, however imperfectly, upon a great man, without
gaining something by him. He is the living light-fountain, which it
is good and pleasant to be near. The light which enlightens, which has
enlightened the darkness of the world; and this not as a kindled lamp
only, but rather as a natural luminary shining by the gift of Heaven; a
flowing light-fountain, as I say, of native original insight, of manhood
and heroic nobleness;--in whose radiance all souls feel that it is well
with them.
