What rhetorical devices are used in "Speech in the Convention" by Benjamin Franklin?

A common rhetorical device in many speeches is the use of parallel structure, and Franklin is no different in this speech. In the third paragraph, Franklin states, "For when you assemble a Number of Men to have the Advantage of their joint Wisdom, you inevitably assemble with those Men all their Prejudices, their Passions, their Errors of Opinion, their local Interests, and their selfish Views." Franklin is arguing that this Constitution cannot be perfect because...

A common rhetorical device in many speeches is the use of parallel structure, and Franklin is no different in this speech. In the third paragraph, Franklin states, "For when you assemble a Number of Men to have the Advantage of their joint Wisdom, you inevitably assemble with those Men all their Prejudices, their Passions, their Errors of Opinion, their local Interests, and their selfish Views." Franklin is arguing that this Constitution cannot be perfect because imperfect men created it, and he then lists some of the men's imperfections.

However, he follows that line with another common feature of speeches, the rhetorical question: "From such an Assembly can a perfect Production be expected?" The purpose of a rhetorical question is to push the audience toward an answer (usually in the negative). In this case, the audience is ready for Franklin's response:

It therefore astonishes me, Sir, to find this System approaching so near to Perfection as it does; and I think it will astonish our Enemies, who are waiting with Confidence to hear that our Councils are confounded, like those of the Builders of Babel, and that our States are on the Point of Separation, only to meet hereafter for the Purpose of cutting one another's throats.

In this quote, one will find another rhetorical technique that sways the audience, the allusion (to the Builders of Babel). Because Franklin's audience would have been Christian, they would understand that the builders of the Tower of Babel were astonished when God made their different languages unintelligible to one another.