Chandrakirti, a Mahayana Buddhist guru, said, "We teach the illusion of existence only as an antidote to the obstinate belief of common mankind in the existence of this world." What he means by this is that the world is only relatively existent in relation to the physical senses and the physical brain. The senses report its existence quite correctly and Mentalism agrees with mankind in the factuality of this experience. But it says this is only a relative truth, that the basic or real truth is that both world and self exist in consciousness, that they are nothing else than Consciousness itself.
-- Notebooks Category 21: Mentalism > Chapter 5: The Key To the Spiritual World > # 135