चातुर्वर्ण्यं मया सृष्टं गुणकर्मविभागशः ।
तस्य कर्तारमपि मां विद्ध्यकर्तारमव्ययम् ॥ ४:१३ ॥

The above verse from Śrīmad Bhagavad Gītā is extremely popular, and is often cited as proof that varṇa comes not from birth but from quality/nature and profession of a person. https://twitter.com/Agent0fChaos_/status/1199680650590052353

Let us see what the verse actually means :

Cāturvarṇyam = 4 varṇas
Mayā sṛṣṭaṃ = created by me
Guṇakarmavibhāgaśaḥ = On basis of classification by Guṇa & Karma
Tasya kartāram = Its cause
mām = is mine
viddhi = know (that)
akartāram = non-caused
avyayam = non-changeable

Put together, it means “The 4 varṇas were created by me based on classification by guṇa and karma. Know that the doing of this creation is mine, and also not mine as I am unchanged by it.”

The meaning of ‘varṇa’ is known to everybody. What about guṇa and karma?

Guṇa refers not to character, but to affiliation with sattva, rajas and tamas, whichever is predominant. Vyāsa has already said in Mahābhārata, “तमः शूद्रे रजः क्षत्रे ब्राह्मणे सत्त्वमुत्तमम् ।“, and Kṛṣṇa will say in B.G 18:41 that “ब्राह्मणक्षत्रियविशां शूद्राणां च परंतप ।

कर्माणि प्रविभक्तानि स्वभावप्रभवैर्गुणैः ॥“ This means 2 things – sattva rajas and tamas will decide the varṇa, and that the 4 varṇas are clearly divided on the basis of past karma, from which the inherent guṇa of a person arises. Thus, varṇa mentioned in B.G 4:13 comes from

past karma and not present activities alone – you can’t choose which karma to accumulate and change your varṇa with it, because your karma from previous births should have allowed it, i.e. made you take birth in a family of that particular varṇa.

“I am unchanged by it” means that although Kṛṣṇa has created the divisions, he himself is unaffected by them. This is because of two reasons – firstly, being Paramātmā he is unaffected by Karma, and secondly, he is not the doer of the actions (as jīvas like us take birth, we

are the ones who perform actions, acquire karma, and take birth, experience pleasures and experience pains accordingly). Thus, we as jīvas are the actual cause of our varṇa, and not God himself. So blaming him if you aren’t born to a rich merchant or a powerful king or a devout

brāhmaṇa is wrong; one should blame himself/herself for it if at all there is anybody to blame.

NOTE: Even if we give in to the ignorant interpretation of guṇa and karma, Kṛṣṇa does not say that we can choose varṇa on that basis; he only says that he created on that basis.

Thus, even under their faulty translation of guṇa and karma, their argument would fail, because saying that they can choose varṇa would imply that they are equating themselves with Bhagavān Kṛṣṇa.