Part of the task of a sermon is to persuade a listener to change his ways or beliefs. Using pathos, Edwards plays upon his audience’s emotions to persuade them to repent from their sins. The most obvious emotion Edwards intends to provoke is fear, but his audience may also have felt guilt about their sins and reluctance to turn to Christ.
So that, thus it is, that natural men are held in the hand of God over the pit of Hell; they have deserved the fiery pit, and are already sentenced to it; and God is dreadfully provoked, his anger is as great towards them as to those that are actually suffering the executions of the fierceness of his wrath in hell, and they have done nothing in the least to appease or abate that anger, neither is God in the least bound by any promise to hold them up one moment.
This section evokes both fear and guilt. How Edwards makes his audience fear is probably evident by now: hellish imagery, the weight of biblical authority, and metaphors that play to their everyday experiences. But notice, as well, that the sinners "deserve" the fiery pit, not only because of their sins but because of their unwillingness to change or ask for forgiveness. The sinners have betrayed God by not taking advantage of his merciful restraint to repent and convert, and they have especially betrayed Jesus, who died for them and can save them from hell, but whom they still scorn. Hearing about God's mercy and Jesus's love, and then hearing how they had caused such distance between themselves and the divine, might have given the audience a guilty conscience. Once the audience is eager to no longer feel fear or guilt, Edwards can more convincingly present a solution: repentance and conversion.