The last instruction is mahājano yena gataḥ sa panthāḥ (CC Madhya 17.186). Therefore you have to follow the footprints of authorities. You can take anyone as you authority, as authority, but according to Bhāgavata there are twelve authorities. That is also mentioned. They are authorized persons from the Supreme Personality of Godhead, and they have got disciplic succession.
The twelve authorities are Brahmā, Nārada, Lord Śiva and Kumāra, Manu and Lord Kapila, Bhīṣma and Prahlāda, Janaka and Yamarāja and this Śukadeva Gosvāmī, who is speaking the Śrīmad-Bhāgavatam, Vaiyāsaki. Vaiyāsaki means "the son of Vyāsadeva." And they have got their disciplic succession. And if we receive that knowledge from disciplic succession, then we can get perfect knowledge. That is the process of Vedic way.
Vedic way is to receive knowledge from the authority, not to manufacture knowledge by mental speculation.