At these moments, America has carried on not simply because of the skill or vision of those in high office, but because We the People have remained faithful to the ideals of our forbearers, and true to our founding documents.
[see grammatical analysis here.]
David Rose wrote to sys-func and Sysfling on 18 March 2015 at 09:15, analysing the above clause complex from Barack Obama's Inauguration Speech:
Now from discourse semantics…
‘America’ and ‘We the People’ are parallel Themes, implying synonymy, implied again graphologically with Caps
‘these moments’ classifies the event (as a national emergency?)
 'America' is not Theme. The first clause has a marked Theme At these moments, which also New, as indicated by the comma marking it off as an information unit. This is grammar, not discourse semantics.
 The fact that two elements are both Themes of their respective clauses does not imply synonymy. Rather, the textual resources of cohesion — in this instance lexical cohesion: synonymy — and Theme can create texture by the way they work together. This is grammar, not discourse semantics.
 The event is the 2009 inauguration of an American president, not a national emergency — a serious misreading of the text, as well as the theory.