Aeolus episode of Ulysses question

I read Ulysses a few months ago (before joining the forum, for certain) and had several questions, one of which concerns this paragraph (which falls beneath the "ITALIA, MAGISTRA ARTIUM" headline in the seventh episode, Aeolus):

"I have often thought since on looking back over that strange time that it was that small act, trivial in itself, that striking of the match, that determined the whole aftercourse of both our lives."

I don't understand this. it doesn't seem like a piece of anyone's consciousness; it is in the past tense; how could it be? But the novel is narrated in third person, so if it's not S.O.C., where did this first person narrator appear from? What it seems [most] like to me is Joyce mocking a popular contemporary novel or play or something; it's very dramatic, and it's not realistic at all to think that one act could determine the course of a life (unlike the novel itself: complete realism).

What does anyone think?

You're right in thinking that the style is dramatic albeit in a very artificial way. Consider where this chapter takes place and then you'll realise why the style is as such.

Remember the shared aims of both Joyce's writing and the genre he parodies. He's making a point about the shortcoming and pretensions of the latter whilst, the former, his style is something that strives to recreate the real and not force upon it things like the embellishment of dramatic style or force it into a conventional plot trajectory.

For in many ways Ulysses has no beginning or end, its a snapshot that acknowledges the existence of that which happened before and that which will happen after the events of 16 June 1904. Remember it borrows heavily from Homer's Odyssey, the epic form which always begins in medias res; in the middle of things.

I think that it IS a piece of someone´s consciousness, namely Stephen´s.

And I´ve looked it up in my annotated student edition (Penguin) and found this (credit it to Declan Kiberd, who wrote introduction and notes:)

"I have often thought ... our lives": A mockery of portentous narrative and (perhaps) a parody of Henry James´s periods. Stephen´s mind appears to be mocking the speaker as he seeks for an 'effect', but, more literally, this may be the precise moment when Stephen chooses the artistic vocation.

I wonder if what this line is sort of a comment on the larger text. It says that the striking of the match affected the course of both of their lives afterwards. REalistically, an act so trivial never seems as if it could have momentous consequences. But, if you look at the text as a whole, it consists of countless little minute details, a blind stripling, one odd word, that recur throughout the entire text. Bloom's confusion and consideration over what the word "parallax" means is very interesting, seeing as the entire book is a series of shifts of perspective--it's ironic that the main protagonist of this parallactic text has trouble grasping the very concept that drives the novel! What i'm getting after is that the minute things, such as Molly's mispronunciation and misunderstanding of "metempsychosis" foreshadows her low-browed prose in the "Penelope" episode; Bloom's helping the blind stripling cross the street, and his visit to Mrs. Purefoy lead us to understand that he holds these humanitarian values that are attempting to convey that Bloom is a hero of the 20th century and someone we should aspire to be. All the minutiae gain momentum and lead to large, meaningful, manifested ends.