The Bhagavad Gita popularized a merit-based guna-karma theory of varna.

Evidence

It was the Bhagvad Gita—which Marxist historian D.D. Kosambi (1962, 16) says was added to the epic Mahabharata “somewhere between 150 and 350 AD”—that made the first popular case for the guna–karma theory. Here, guna means intrinsic qualities or attributes, and karma is actions. Much before the Gita, around the second century BCE, the Samkhya school of upanishadic philosophy propounded the tri-guna theory, the three gunas being sattva (corresponding to clarity of thought and purity of mind, associated with the Brahmin), rajas (passionate, excitable state of mind, associated with the Kshatriya) and tamas (darkness, a state of confusion, associated with the Shudra). — Ambedkar, B R, Annihilation of Caste_ The Annotated…, 1181

Categorization

• DEFINE: Defines the three gunas (sattva, rajas, tamas) and maps them to the caste hierarchy.
• XREF: Directly relevant to the reader’s purpose on caste annihilation: this merit-based reading is the key ideological defense of varnashrama against birth-based caste, which Ambedkar dismantles.