In "Sinners in the Hands of an Angry God," what is the writer's main purpose?

Jonathan Edwards’s main goal in writing and delivering his sermon “Sinners in the Hands of an Angry God” was to persuade people to love God and give their hearts to him.  If they do this, Edwards believes they can be saved.
Before the Great Awakening (of which Edwards was a part), many religious Americans believed in predestination. They believed God had already decided whether they were going to Heaven or Hell and that there was nothing they could do to change their fate. Preachers of the Great Awakening disagreed. They believed people deserved to be damned but could save themselves by accepting God’s love and loving God in return. 
The main purpose of Edwards’s sermon is to convince the people who are listening that this is true. He warns them about how they are in danger of going to Hell, and claims they would completely deserve that fate. He says, there is an opportunity for them, though; they can accept God and improve their chances for salvation. Edwards tells his listeners that God has given them

an extraordinary opportunity, a day wherein Christ has flung the door of mercy wide open, and stands in the door calling and crying with a loud voice to poor sinners.

He tells them that many other people have already accepted God’s love and that their

hearts [are] filled with love to him that has loved them and washed them from their sins in his own blood, and rejoicing in hope of the glory of God.

He urges them to do the same so they might be saved as well and be able to live with God in Heaven. His main goal in this sermon is to get people to accept God’s love and to love him back so they can be saved from damnation.