But what was the explanation for God’s own existence? Leibniz had an answer to this question too. Unlike the universe, which exists contingently, God is a necessary being. He contains within Himself the reason for His own existence. His nonexistence is logically impossible. Thus, no sooner was the question Why is there something rather than nothing? raised than it was dispatched. The universe exists because of God. And God exists because of God.
NB - Avicenna came up with list idea centuries before Leibniz
