"The Universe is Mental--held in the Mind of THE ALL." -- The Kybalion

According to the Hermetic Philosophy, existence is a dream in the mind of God. If you want more details, you should read The Kybalion.

We are much like mini-Gods who are also capable of creating universes inside our minds, which we call dreams. We are also capable of holding "our reality" as a universe inside our mind. As within, so without.