Parallelism is used in “Sinners of an Angry God” primarily as a means of driving home the sermon's main point: that God can, and will, consign to Hell anyone he so chooses at any time. The repeated grammatical structures that parallelism involves have the effect of sending home a message and, in so doing, giving it greater power. A message given once in the course of a speech would almost certainly not have the same effect or anything like it. But as the message of Edwards's sermon is so important, it needs to be asserted again and again, and this is where parallelism comes in useful.

In one particularly powerful passage, Edwards reminds his audience that if

your strength were ten thousand times greater than it is, yea, ten thousand times greater than the strength of the stoutest, sturdiest devil in hell,

it would not be enough to withstand God's terrible wrath.

What Edwards is doing here is to make clear once again the relative insignificance of humanity by comparison with the Almighty. No matter how strong we are and no matter how strong we think we are, our strength is as nothing compared to the wrath of God, which can consign us to the fiery pits of Hell at a moment's notice. Even if we could somehow increase our strength by ten thousand fold, it still wouldn't make any difference. That is because, as the title of the sermon tells us, we are sinners in the hands of an angry God.

Parallelism is a useful literary device in sermons and other persuasive works. Because of its rhythm and balance of grammatical structure, as well as its repetition of ideas, parallelism produces a powerful and lasting impression upon the listener. Jonathan Edwards makes use of this literary device in his emotionally stirring sermon, "Sinners in the Hands of an Angry God."

In his sermon, the Reverend Edwards employs parallelism, lending his words power as all phrases are equal in their importance and impact. Here is an example from an early part of his sermon:

The devil is waiting for them [the sinners], hell is gaping for them, the flames gather and flash about them.

This use of parallelism strongly emphasizes the idea that sinners live on the brink of hell, as well as describing some of the horrors that await them. Further in his sermon, the Reverend Edwards describes hell in more frightening terms, again using parallelism:

That world of misery, that lake of burning brimstone, is extended abroad under you....
There is the dreadful pit of the glowing flames of the wrath of God; there is hell's wide gaping mouth open....there is nothing between you and hell but the air...

Although the Reverend Edwards addresses respectable, church-going people, he uses parallelism to impress upon them that they are, nevertheless, "abominable" in God's sight. In his sermon, Edwards's graphic descriptions and parallel structures that repeat and emphasize ideas help to exaggerate his views of the dangers of eternal damnation. Such rhetorical devices strengthen his efforts to sway his audience.

In order to understand how Jonathan Edwards uses parallelism, one must first understand the context of the piece.  First, this text is a sermon, an oral piece meant to be heard, not read.  So speakers use particular techniques to aid their listeners in remembering the message being presented.  Parallelism is one of those techniques (along with repetition and imagery).  

Second, Edwards uses parallelism for different purposes for his message.  For instance, Edwards proclaims to the church congregation: "The Wrath of God burns against [the unconverted], their Damnation don’t slumber, the Pit is prepared, the Fire is made ready, the Furnace is now hot, ready to receive them, the Flames do now rage and glow."  Here, Edwards is describing, metaphorically, to his audience about the imminent danger that is God's wrath and the fires of Hell.  By listing all the ways that the unconverted are nearing their doom, he is emphasizes the urgency for sinners to change their ways.

Another way that Edwards uses parallelism is through the logical appeal.  Because Edwards wants to convince his audience to convert immediately to a more Christian life, he must not just scare them into converting but also convince them through rationalization: "The bigger Part of those that heretofore have lived under the same Means of Grace, and are now dead, are undoubtedly gone to Hell: and it was not because they were not as wise as those that are now alive: it was not because they did not lay out Matters as well for themselves to secure their own escape."  In this example, Edwards gives evidence as to how those who appear on the outside to be good and holy are not necessarily saved from God's wrath.  This evidence may not be proven factually, but because the congregation is comprised of believers who invited Edwards to preach to them, then he will convince them with this logic.

How does Jonathan Edwards use imagery in "Sinners in the Hands of an Angry God"?

Jonathan Edwards's use of imagery in "Sinners in the Hands of an Angry God" is primarily intended to make his message more striking and urgent. Edwards achieves this by using simple objects and situations with which his hearers would have been familiar and building metaphors and similes from them. He describes God holding the sinner over the pit of hell as being like a person who is about to throw a spider into a kitchen fire. This is a vivid, clear comparison which drives home the message of how precarious the sinner's position is, since it is far more likely that someone holding a spider over a fire will let it fall into the flames than it is that they will have a change of heart and decide to rescue it.

The same effect is accomplished by the image of divine justice setting an arrow to a bowstring and aiming it at the sinner's heart. The image is a familiar one, and the sense of danger is palpable. The archer aiming at a target hardly ever decides not to shoot after all unless something unusual happens. By far the most likely outcome is that the shot will be fired, and divine justice will not miss the mark.