The Chandogya Upanishad is widely held to “predate” Buddhism, and this is almost certainly so, but it is a mistake to take any particular verse in the Chandogya and assume that it is by definition earlier than any particular verse in Buddhism.
Take the case below:
Tena kho pana samayena brāhmaṇassa pokkharasātissa ambaṭṭho nāma māṇavo antevāsī hoti ajjhāyako mantadharo tiṇṇaṁ vedānaṁ pāragū sanighaṇḍukeṭubhānaṁ sākkharappabhedānaṁ itihāsapañcamānaṁ padako veyyākaraṇo lokāyatamahāpurisalakkhaṇesu anavayo anuññātapaṭiññāto sake ācariyake tevijjake pāvacane:
Now at that time Pokkharasāti had a student named Ambaṭṭha as his resident pupil. He was one who recited and remembered the hymns, and had mastered in the three Vedas, together with their vocabularies and ritual performance, their phonology and word classification, and the testaments as fifth. He knew them word-by-word, and their grammar. He was well versed in cosmology and the marks of a great man. He had been authorized as a master in his own tutor’s scriptural heritage of the three Vedas with the words:“yamahaṁ jānāmi taṁ tvaṁ jānāsi;
“What I know, you know.yaṁ tvaṁ jānāsi tamahaṁ jānāmī”ti.
And what you know, I know.”
DN3
VS
॥ सप्तमोऽध्यायः ॥
अधीहि भगव इति होपससाद सनत्कुमारं नारदस्तं होवाच यद्वेत्थ तेन मोपसीद ततस्त ऊर्ध्वं वक्ष्यामीति स होवाच ॥ ७.१.१ ॥
|| saptamo’dhyāyaḥ ||
adhīhi bhagava iti hopasasāda sanatkumāraṃ nāradastaṃ hovāca yadvettha tena mopasīda tatasta ūrdhvaṃ vakṣyāmīti sa hovāca || 7.1.1 ||
Nārada went [for spiritual instruction] to Sanatkumāra and said, ‘Sir, please teach me.’ Sanatkumāra said to him: ‘First tell me what you know already. I’ll teach you from that point.’ Nārada said—
ऋग्वेदं भगवोऽध्येमि यजुर्वेदं सामवेदमाथर्वणं चतुर्थमितिहासपुराणं पञ्चमं वेदानां वेदं पित्र्यं राशिं दैवं निधिं वाकोवाक्यमेकायनं देवविद्यां ब्रह्मविद्यां भूतविद्यां क्षत्रविद्यां नक्षत्रविद्यां सर्पदेवजनविद्यामेतद्भगवोऽध्येमि ॥ ७.१.२ ॥
ṛgvedaṃ bhagavo’dhyemi yajurvedaṃ sāmavedamātharvaṇaṃ caturthamitihāsapurāṇaṃ pañcamaṃ vedānāṃ vedaṃ pitryaṃ rāśiṃ daivaṃ nidhiṃ vākovākyamekāyanaṃ devavidyāṃ brahmavidyāṃ bhūtavidyāṃ kṣatravidyāṃ nakṣatravidyāṃ sarpadevajanavidyāmetadbhagavo’dhyemi || 7.1.2 ||
Sir, I have read the Ṛg Veda, the Yajur Veda, the Sāma Veda, and the fourth—the Atharva Veda; then the fifth—history and the Purāṇas; also, grammar, funeral rites, mathematics, the science of omens, the science of underground resources, logic, moral science, astrology, Vedic knowledge, the science of the elements, archery, astronomy, the science relating to snakes, plus music, dance, and other fine arts. Sir, this is what I know.
Now it seems that the Buddhist text was set when there where only 3 official Vedas, and substantially fewer auxillary sciences, it therefore appears likely that the Upanishad reached it’s editorial closing at a later point than the Buddhist text.
However we are unable to infer anything about the actual composition dates in a comparitive sense, as the Upanishad may have originated in a “three veda” era and merely been updated as the vedas and sciences grew, while the Buddhist text, being less conscerend with the particulars of Brahminism perhaps didn’t bother.
At any rate, there seems to be plenty of nuance to be had before one confidently asserts that “such and such a text” is “pre-buddhist”.
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