What does non-chronological storytelling tell us about the nature of cinema?

When the first screenwriting manuals were written, in the years around the First World War, they took most of their aesthetic and structural cues from existing manuals on playwriting. These followed on from the writers who had established the ‘rules’ of the well-made play - British authors tended to quote William Archer, Americans Brander Matthews. Frances Taylor Patterson, writing in 1921, advises budding screenwriters to ‘consort with the master minds of dramatic criticism. From the Stagirite [Aristotle] to Sarcey, from Brunetiere to Brander Matthews’
However, where the narrative cinema took most of its rules from the nineteenth century theatre, there was (and remains) a striking exception to this. Non-chronological storytelling was rare in the theatre – here the cinema was more influenced by the novel, and in particular the expository flashbacks found in Victorian novels such as A Study in Scarlet (1887). David Thomson makes the connection explicit in How to Watch a Movie:
‘Once upon a time, the flashback was like a found object, a vital cache of letters or information, an answer in the mystery of story, a tidy package of life or action, introduced for its explanatory value.’
In 1928, Eric Elliott wrote of the way in which theatre writers were beginning to adopt cinematic techniques, such as non-chronological act order, and discussed the way in which the younger medium was affecting the older.
The question here that interests me is why, in its two millennia of existence, the theatre didn’t invent (or at least make greater use of) the flashback until prompted to do so by the cinema, and what this tells us about both media. The answer, I would suggest, is connected with their relationship with time.
The theatre is, broadly speaking, a medium that exists wholly in the present tense – actors and audience share space and time, and we are conscious of the events as taking place in front of us, even if they represent another era. This contrasts it with the written word, which (generally) uses the past tense to describe events that have already taken place.
The cinema seems to me to exist in a curiously ambiguous relationship between the two – as an audience, we are conscious that we are watching something that pre-exists, but we watch it (especially if in a cinema) in the present tense. Non-chronological storytelling emerged out of this ambiguity, and grew with the medium.
My paper will examine the way in which this process took place, and what this tells us about the cinema. I will also look at cases where the relationship between past and present tenses are problematised, such as live cinema, silent film with live accompaniment, and live-streamed theatre.