Atman in Sanatan Dharma defines the breathing one. The one true being residing inside every living being present on this planet. Our Upanishads states atman as eternal and supreme creation living beyond the physical world. After a person dies in the real world (Earth), their atman moves to the afterlife to be reborn as a new individual.
Sanatan Dharma believes in the cycle of birth and death where a person will die to be born again as another creature. This cycle continues until the atman realizes the truth of its origin and works to attain salvation (moksha).
Relation between Atman and Brahman
Brahman, or we can say, the Universe is an unchanging conscious spirit that consists of atman. According to the concept of Sanatan Dharma, when a person dies, the atman moves to the afterworld leaving the physical body to submit itself to the Brahman.
The soul of an individual is Jeevatma, while the universal soul is Paramatma. The supreme purpose in Hinduism is to dissolve one’s Jeevatma into Paramatma. However, if an atman achieves moksha or liberation from the world of illusion, then it becomes the Brahman itself. It becomes easier to achieve moksha if you practice ethical living following dharma (duty) and karma (actions).
The context about atman has its mentioning in the Rig Veda(1.10.97-11) in the forms of hymns and songs written in the Sanskrit language. Further, discussions on atman are present in the Upanishads. It is in the form of a conversation among a guru and its disciples. There are over 200 Upanishads that consist of metaphysical questions and their answers.
Moving forward in understanding Atman, Upanishads explains Brahman and Atman, made up of the same substance, and after moksha, atman dissolves back into the Universe.
The Chandogya Upanishad has a beautiful passage that explains the concept through lines of poetry where Uddalaka is explaining his son, Shvetaketu:
Science and Scientists in Sanatan Dharma
You all might know about the famous Physicist Erwin Schrodinger and his cat. The Physicist did great work in the field of science. Moreover, when scientists often Dizz religion, Schrodinger was influenced by Hindu Scriptures. In his biography, you will realize his works had an influential touch of Hinduism.
“From the earliest great Upanishads, the recognition Atman = Brahman (the personal self is equal to the omnipresent, all-encompassing eternal self) regarded in Indian thought, far from being blasphemous, representing the quintessence of deepest understanding of events of the world. Of all students of Vedanta after learning to pronounce with their lips, precisely to assimilate in their minds this great of all thoughts”. [Excerpt from an essay on determinism and free will.”
Earlier, scientists forbid studying the soul as it seems antagonistic. But, after studying the soul, science has started considering the soul has materialistic existence. Thus, it can get detected through devices. Further, the scientists conclude the study of the soul by stating the concept of electromagnetic signals for detecting the soul. It is the first step taken by modern scientists to understand the science behind the existence of atman.