If God has already willed to send rain, then why pray for it? Or if God has chosen to save you, then why fight so hard against temptation?
Edwards gives his answer to questions like these in Miscellanies #29 (reformatted for readability):
God decrees all things harmoniously and in excellent order; one decree harmonizes with another, and there is such a relation between all the decrees as makes the most excellent order. Thus God decrees rain in drought because he decrees the earnest prayers of his people; or thus, he decrees the prayers of his people because he decrees rain.
I acknowledge, to say God decrees a thing "because," is an improper way of speaking, but not more improper tha…