why do u think Edwards felt it was necessary to terrify his puritan audience into action?

Answer 1

Johnathan Edwards apparently believed the nature of people was sinful, and given their own choices, sin was their calling. He aimed for a higher calling, a "puritanical" state, which was not their nature, so he scared the hell out of them, thinking that would do it.
http://www.jonathan-edwards.org/Sinners.html
This is my opinion. Others are not so charitable to Edwards motives....
<<Later writers, notably Professor Perry Miller, have corrected this account in certain respects. College students, introduced to Edwards via other routes than the sermon on "Sinners in the hands of an angry God," can set Phyllis McGinley right. But in the main the judgment stands in America, in American Protestantism, in literary and academic, even in most theological circles: Jonathan Edwards was a great man, but he was wrong on almost every issue for which he contended -- the gloriousness of inscrutable, almighty, universal, majestic, wrathful God; the depravity and corruptness of the human heart; the need for the reconstitution of the church not as catholic and all-inclusive but as the selected group of the convinced; the determinism, the unfreedom of human existence; the glory of God as the chief and only end of being, which in reconciliation man serves willingly as a "cosmic patriot," but will serve in his unwillingness by his destruction, as Hitler's patriots in their catastrophic ending may be said to glorify the rule of justice.>>

I agree with the latter, Edwards got it wrong, as did Hitler...and Stalin...and many others, and in them, I see little difference. Remember, it was Hitlers National Lutheran church which stood against the Jews. In Stalin's reign, it was his wannabes, the Communist parties, which stood against believers. In Edwards time, he stood against those who believed in a loving and just God.

Answer 2

Do you think he wanted to scare the hell out of his audience?

Answer 3

One additional thought on this, the jist of Edwards' failure. Over the years, I have greatly altered my leadership and management style. I started as a role model for the autocratic know all the answers leader. I am now in the style of the servant leader...one who gets others to get things done by serving, and facilitating them. What motivated me to make the change: I discovered there are two things which motivate people:
a) the need to grow
b) the need to avoid pain

Of these, the most powerful, and lasting motivation is based on giving people growth opportunities. If you are leading or managing by scaring them, you are appealing to the b) tactic, and they will do a minimal amount of effort to "do the task", but they will seek growth opportunities elsewhere. This, in fact, is Edwards folly: He scared the Hell out of them, but they were not motivated to stay away from Sin.

All of us need to grow, and see positive opportunities if we are to grow.