Backshifting of tenses: We have discussed the deictic shifting of adverbial and PrepP time expressions in S,E,R terms. Can the same now be applied to the backshifting of verb tenses, too? Evidently, people prefer to shift as follows when speaking 'precisely':
Original sentence: "Jane left".
Report: either Mary says that Jane left.
or Mary said that Jane had left.
(where, in precise speech, both are preferred to Mary said that Jane left.)
Original sentence: "I will do it."
Report: either He says (that) he'll do it.
or He said (that) he'd do it.
(where, in precise speech, both are preferred to He said (that) he'll do it.)
Can this preference be modeled according to a general principle of shifting within S,E,R? That is, what is happening when we backshift? Why would we disprefer a report that does not utilize backshifting? Can we apply Fillmore here (or the somewhat more precise formulation of Reichenbach)?