The third sutra, Sastrayonitvat, sharpens the insight of the previous aphorism by stating even more firmly that Brahman is known only through scripture. If the earlier sutra identified Brahman as the source, sustenance, and dissolution of the universe, this one clarifies the means by which that truth is established: not by independent reasoning, but by the revealed authority of the Srutis.
The central question here is epistemological. Since Brahman already exists, one may object that It should be knowable like any other existing thing—through perception, inference, comparison, or other ordinary means of knowledge. Vedanta responds by showing why Brahman is unique. Unlike a visible object, Brahman has no form, colour, or sensory qualities that can be directly perceived. It is not an object among objects.
Nor can Brahman be securely established by inference alone. Inference depends on inseparable signs, like smoke indicating fire. But Brahman, being beyond all empirical marks, provides no such directly observable sign that reason can independently seize upon. Analogy too fails, since there is nothing truly comparable to the infinite and absolute.
For this reason, the sutra teaches that scripture is the sole primary source of knowledge regarding Brahman. The Upanishadic revelations do not merely suggest Brahman; they disclose That which lies beyond the reach of the senses and the categories of ordinary thought. The scriptures themselves declare that without revelation, Brahman cannot be truly known.
This does not reject reason entirely. Once Brahman has been revealed through the Vedantic texts, reflection and reasoning may still serve an important role. Their task, however, is secondary and supportive: they help unfold the meaning of the scriptural declarations, remove doubt, and stabilise understanding. They do not independently establish Brahman, but illuminate what the scriptures have already made known.
The sutra therefore marks a profound principle of Vedanta: ultimate reality is not discovered as an external object, but disclosed through sacred revelation and then realised inwardly through reflection. Scripture is thus the womb of Brahma-knowledge, the sacred source from which liberating insight is born.
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