Question

how do the syntax and rhetorical features that jefferson uses in the first sentence of the second paragraph contribute to the persuasiveness of the document

Answer 1

What he does is use different lexical items than the usual ones to present it as a noble endeavor. "We hold these truths to be self-evident" sounds much better than "We believe". In addition, he also uses the word "that" to present it in a rhythmical and a powerful way.