Step 1: Understanding the Concept:
Chapter 15 of the Bhagavad Gita, titled Purushottama Yoga, begins with a powerful metaphor of an inverted Ashvattha (Peepal/Fig) tree. This metaphor is also found in the Katha Upanishad. It is used to illustrate the complex, entangled, and transient nature of material existence and its divine origin.
Step 2: Detailed Explanation:
The verse 15.1 states:
"ūrdhva-mūlam adhaḥ-śākham aśvatthaṃ prāhur avyayam |
chandāṃsi yasya parṇāni yas taṃ veda sa veda-vit ||"
Translation: "They speak of the eternal Ashvattha tree, which has its roots above and its branches below; its leaves are the Vedic hymns. One who knows this tree is a knower of the Vedas."
- Urdhva-mulam (Roots Above): The 'roots' represent the Supreme Brahman or God, who is transcendental and 'above' the material world. Just as a tree depends on its roots, the world depends on Brahman.
- Adhah-shakham (Branches Below): The 'branches' represent the various levels of material creation (the worlds of demigods, humans, and lower beings).
- Ashvattha: The word means "that which does not remain the same tomorrow" ($a$ = not, $shvas$ = tomorrow, $tha$ = remains), signifying the transient nature of the world.
This metaphor describes Samsara (the cycle of birth and death/material existence). The purpose of knowing this tree is to learn how to cut it down using the "axe of detachment" (asanga-shastrena) to attain liberation.
Step 3: Final Answer:
The inverted tree describes the nature of Samsara (the world/existence).