Berkeley's immaterialism, in my opinion, has its main source in a reliable, ­personal, self-evident experience of God's presence in human existence. Contrary to other modern philosophers, who introduce the notion of a Supreme Being in order to solve substantial problems in their systems, Berkeley's attitude of mind seems near to the common religious feeling of a familiar and actual proximity of the divinity to man in everyday life.Indeed there is no need to prove God's existence: "I am certain there is a God, though I do not perceive him and I have no intuition of him" (Philosophical Commentaries, 813).