Immaterialism: Berkeley’s philosophical theory, known as “Immaterialism” is a notion that everything we perceive is an idea that belongs to minds and cannot have an existence independent of minds. It denies the existence of matter or material substance. The summary of his theory in motto “esse est percipi” or “To be is to be perceived”. Basically, what we have is only ideas in the mind; and there are no material objects. Therefore, only ideas that we perceive in the mind are real.
Berkeley also argued for Idealism – a concept that mind constitutes the Ultimate Reality. Since an idea depends on mind and has no independent existence of its own, any thing that exists depends on how it is being perceived. And mind is the single substance that has its independent existence and infinite in nature. Thus, it is God.