SELF-ENQUIRY

Ramana Maharshi advocated self-enquiry as the principal means to gain insight:  Enquiry in the form of  "Who am I?" is the principal means, he said.

The answer to the question "Who am I?" is found in one's own heart, but also in four Vedas:

To begin with, "Consciousness is Brahman," in the Aitareya Upanishad of the Rig-Veda. 

Secondly, "I am Brahman," in the Brihadaranyaka Upanishad of the Yajur Veda. 

Thirdly, "That thou art," in the Chandogya Upanishad of the Sama Veda. 

Fourthly, "This self is Brahman," in the Mandukya Upanishad of the Atharva Veda.

These statements in the Vedas are called "mahavakyas," translated as "great sayings."  A mahavakya is a concise Vedantic formula, or mantra, pointing out the oneness of the individual soul with Brahman.