The Vedas were not composed by anyone.
Apaurusheya — not of human authorship, and without beginning: heard rather than written, and preserved by sound long before sense. Accepting their authority is the classical test of orthodoxy, which is why almost every Hindu affirms it and almost none has read them.
Apaurusheya is a stronger claim than divine inspiration. The Veda is not revealed by God to a prophet in this account; it has no author at all, God included, and exists the way mathematics might be said to exist. Mimamsa built an entire philosophy of language to defend it, arguing that the connection between a word and its meaning is eternal rather than conventional. The practical consequence was a transmission system of astonishing fidelity: layered recitation patterns that scramble word order deliberately so errors cannot propagate, and priestly families that could recite thousands of verses with the pitch accents intact without knowing what many of them meant. Accepting Vedic authority is what makes a school astika rather than nastika, which is how Buddhism and Jainism ended up outside. Lingayats reject it explicitly and are counted Hindu anyway, which tells you how much the formal test governs.
That which is, is one; the wise speak of it in many ways.
Rig Veda 1.164.46 (rendered)The most quoted half-line in Hinduism, and the one every pluralist argument starts from.
The same ground, other faiths
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