Hinduism is the predominant and indigenous religious tradition of the Indian Subcontinent. Hinduism is known to its followers as Sanatana Dharma (“the eternal law”). Hinduism is formed of diverse traditions and has no single founder. A large body of texts is classified as Hindu, divided into Sruti (“revealed”) and Smriti (“remembered”). Among these texts, the Vedas are the foremost in authority, importance and antiquity. Other major scriptures include the Upanishads, Puranas and the epics Mahabharata and Ramayana.
Etymologically, the Sanskrit word “Upanishads” suggests “sitting down near,” as in a disciple sitting at the feet of his master. This is a common form of Hindu instruction to this day. The teaching is, accordingly, presented in dialogue form; a wife speaking to her husband or a son to his father. Through common interaction, the Upanishads weave the most profound instruction.

Upanishads on Know Thyself

The Katha Upanishads portrays a story of Yama (or Death) teaching a young and curious boy called Nachiketa about the mysteries of the Self. Nachiketa, having witnessed his father’s pointless traditional observance of Hindu custom, inquires with Yama whether it is possible to survive death, and if so, by which means. A profound dialogue follows, centered around the Self:

Katha Upanishad: The Self lies beyond the senses and can only be understood by him who knows It is.
Katha Upanishad: Those who realize the Self are forever free from the jaws of death.

“This doubt haunted even the gods of old,” says Yama to Nachiketa, “For the secret of death is hard to know.” In the course of the dialogue, Yama draws a line between the body, which experiences reality through the senses, and the spirit, which transcends sensual perception. “[Those] hypnotized by the world of sense [say], ‘I am my body; when my body dies, I die.’ Living in this superstition, they fall life after life under my sway.”
According to Yama, the key to surviving death is transferring one’s identity from the bodily senses to the metaphysical Self. ” Well have you renounced these passing pleasures so dear to the senses,” he tells the young boy, “And turned your back on the way of the world that makes mankind forget the goal of life.”

A sage withdrew his senses from the world
Of change and, seeking immortality,
Looked within and beheld the deathless Self.
The Self is the goal of life; attain this goal.

Yama outlines a specific practice for this end, and names it after the courageous young boy Nachiketa. This would lay the foundation for subsequent Indian ritual and exercises, such as meditation and recitation of mantras.

Those who know the Self become the Self.

Knowing the Self

Knowing the Self is the underlying current of the Upanishads, presented as the ultimate goal of life. Thus does a Hindu teaching, far away in space and time from Classical Greece, coin the very same wisdom as conveyed from the Socratic dialogues. After all, what is objectively true must hold true for all people in all times. If, indeed, is self-knowledge is truly the essence of all knowledge, all cultures and civilization who genuinely inquired in the nature of truth must have found similar results.

Ramayana: Enquiry into the truth of the Self is knowledge.

Further Reading:
Bhagavad Gita on Know Thyself
Confucius on Know Thyself
Zen Masters on Know Thyself