Out of the four mahavakyas—great sayings—that sum up the teachings of the Upanishads, the most famous, after ‘aham brahmasmi’, is ‘tat tvam asi’. The literal meaning of this is—that you are. This sentence is found in the Chandogya Upanishad, one of the earliest Upanishads, written more than 2,500 years ago. It was spoken by Uddalaka Aruni, a revered Vedic sage from the Kuru-Panchala region. His name is also mentioned in the Mahabharata. In fact, Mahabharata has an interesting story about how he got his name.
A young Aruni was a disciple of the sage Ayoda-Dhaumya. One day, Aruni was asked by the Guru to go to the fields because a breach had taken place in the canal carrying water to the fields. Aruni tried to plug the breach using mud and stones but it was too big. Aruni then laid his body down against the breach and the water flow was stopped. When Aruni did not return by evening, his Guru, along with his other students, set out in his search. He found Aruni lying in the breach. Because of his loyalty to his Guru, Aruni became known as Uddalaka.
Aruni became a famed teacher himself. He is counted among the first philosophers and natural scientists in recorded history. When his son Svetaketu returned home at the age of 24 and learned all the Vedas, Aruni asked him if he had received the ultimate knowledge. Svetaketu was not sure what knowledge that was.
Aruni said, ‘Bees produce honey by gathering together the nectars from the flowering trees in every direction, and those nectars become one single honey. Just as those nectars do not get the idea which tree they have come from, in the same way, all these beings, having sprung from the Supreme Being, do not know they have sprung from Him. Whatever they are in this world—tiger, lion, wolf, bear, worm, flying insect, biting insect, or mosquito—that they become. That which is the finest essence, the whole universe has That as its soul. That is Reality, That is the Self, and That is you.’
‘Tat tvam asi’ reveals a great truth about the underlying unity in this world. Every living being in this world is a form of the Supreme being. That means there is no difference between our soul and the Supreme Soul, and also that of another human being—no matter which caste, creed, race, religion, or nationality, they belong to. Indeed, there is no difference between the souls of humans and animals. If we were to understand this mahavakya of the Upanishads, it would be very easy for us to peacefully co-exist with others in this world.