Full Idea
By this principle alone, that there must be a sufficient reason why things are thus rather than otherwise, I prove the existence of the Divinity, and all the rest of metaphysics or natural theology.
Gist of Idea
The existence of God, and all metaphysics, follows from the Principle of Sufficient Reason
Source
Gottfried Leibniz (Letters to Samuel Clarke [1716], §2)
Book Reference
Leibniz,Gottfried: 'Philosophical Writings', ed/tr. Parkinson,G.H.R. [Dent 1973], p.207