The general theme is the power of God’s will versus the power of human beings to resist temptation and avoid damnation through their own efforts. Edwards’ intent here is, to borrow a phrase from Reinhold Niebuhr, to “afflict the comfortable” – to unsettle his congregation to the extent that they will understand that in his view their comfortable lives have nothing to do with their own efforts and everything to do with God’s sovereign will:
… you find you are kept out of Hell, but don’t see the Hand of God in it, but look at other Things, as the good State of your bodily Constitution, your Care of your own Life, and the Means you use for your own Preservation. But indeed these Things are nothing; if God should withdraw his Hand, they would avail no more to keep you from falling, than the thin Air to hold up a Person that is suspended in it.
Edwards exhorts his audience to understand that only a direct experience of God – being “born again” and experiencing what he refers to as the “Great Change of Heart” (the focus of the Great Awakening) – can keep one from God’s wrath, and that merely observing the forms of religion and righteousness are useless exercises. It isn't enough to simply go to church and mouth the right words – one must undergo what Edwards considers a genuine conversion experience to save himself from the fury of God.
In his sermon, Edwards is works to bring his audience to God. A part of the Great Awakening, Edwards is sharing with his congregation- and those who may have moved from the Puritan way of life. He reminds (and frightens) his congregation into returning to the church and a holy way of life.
Edwards tells his parishioners that they only reason they are alive and the only reason they woke up this morning is because God allowed them to. He paints a scary image of a spider hanging over the fiery pit of hell. Here the Puritans are the spider and God is the string protecting them. He warns that death could come at any moment, and so the only way to be saved, truly saved, is to repent and return to the church.