By study of Sankhya, one understands the course of evolution. By study and practice of Yoga, one gains self-restraint and obtains mastery over mind and senses. Some of the doctrines of the Nyaya, the Vaiseshika, the Sankhya and the Yoga are opposed to the teaching of the Vedas. These systems are only superficially based on the Vedas. The Nyaya and the Vaiseshika schools rely too much on human reason, though they accept the Vedas as the supreme authority.
Human intellect is frail and finite.
It has got its limitations. It functions within time, space and causation. Its findings cannot be infallible. It cannot solve transcendental matters. Vedas only are infallible and authoritative.