Vedic knowledge is infallible, it is given by infallible God himself

Vedic knowledge is infallible because it comes down through the perfect disciplic succession of spiritual masters, beginning with the Lord Himself. Since He spoke the first word of Vedic knowledge, the source of this knowledge is transcendental. The words spoken by the Lord are called apauruseya, which indicates that they are not delivered by any mundane person. A living being who lives in the mundane world has four defects: (1) he is certain to commit mistakes; (2) he is subject to illusion; (3) he has a propensity to cheat others; and (4) his senses are imperfect. No one with these four imperfections can deliver perfect knowledge. The Vedas are not produced by such an imperfect creature. Vedic knowledge was originally imparted by the Lord into the heart of Brahma, the first created living being, and Brahma in his turn disseminated this knowledge to his sons and disciples, who have handed it down through history.

– Srila Prabhupada, Sri Isopanishad Mantra 1 purport