Full Idea
My system of Pre-established Harmony furnishes a new proof of God's existence, since it is manifest that the agreement of so many substances, of which the one has no influence upon the other, could only come from a general cause on which they all depend.
Gist of Idea
All substances are in harmony, even though separate, so they must have one divine cause
Source
Gottfried Leibniz (Principle of Life and Plastic Natures [1705], p.192)
Book Reference
Leibniz,Gottfried: 'Leibniz Selections', ed/tr. Wiener,Philip P. [Scribners 1951], p.192
A Reaction
Adjacent harmony seems self-explanatory, but remote harmony is interesting evidence for God. Hence modern quantum non-locality should make us all wonder whether there is a deeper explanation.