According to Jonathan Edwards in “Sinners in the Hands of an Angry God,” the only thing that keeps people out of hell is God’s mercy. We can see this in many places in the sermon. Here are two examples:
…'tis to be ascribed to nothing else, that you did not go to hell the last night; that you was suffered to awake again in this world, after you closed your eyes to sleep: and there is no other reason to be given why you have not dropped into hell since you arose in the morning, but that God's hand has held you up.
There is nothing that keeps wicked men, at any one moment, out of hell, but the mere pleasure of God.
In other words, everyone would be in hell if God did not have mercy on them and hold them out of the fire.
When Edwards preached this sermon, he was trying to instill greater religious fervor in his audience. At that time, the Puritans of New England had, in general, been becoming less religious. People were being admitted into the church without having had a genuine conversion experience (this was called the Halfway Covenant). The church had to do this because too few people had enough religious zeal to undergo such an experience. What this meant is that the members of the church did not feel as attached to their religion as their forebears had.
In order to remedy this, Edwards emphasized the fact that all humans deserved to go to hell. He argued that there was nothing a person could do to deserve salvation. The only thing people could do was to be converted to a deep and emotional love of God. They had to be grateful to God for not allowing them to be cast into hell as they deserved. They had to have
their hearts filled with love to him that has loved them and washed them from their sins in his own blood.
This was why Edwards emphasized that only God’s mercy kept sinners (which includes all living people) out of hell.