The Vedas says, tad-vijñānārthaṁ: "In order to know that transcendental science," sa gurum evābhigacchet, "he must go to a guru. He must approach." A guru means not bogus guru. One who knows, expert. But one has to do that. There is no other alternative. That is the injunction of every Vedic śāstra. And this order is from the Kathopaniṣad. Then, on the Bhagavad-gītā the same thing is said, tad viddhi praṇipātena (BG 4.34).
Praṇipāta means surrender. Surrender where? Where to surrender? To a coolie? No, to a superior person, guru. Similarly, Bhāgavata says, tasmād guruṁ prapadyeta jijñāsur śreya uttamam (SB 11.3.21): "One who is inquisitive to understand the spiritual science," tasmād, "therefore," guruṁ prapadyeta, "must surrender to a guru." Just our this morning prayer is guru, beginning of life, beginning of day's work, first worshiping guru.
- saṁsāra-dāvānala-līḍha-loka-
- trāṇāya-kāruṇya-ghanāghanatvam,
- prāptasya kalyāṇa-guṇārṇavasya
- vande guroḥ śrī-caraṇāravindam
So in our this Vedic way of life, to accept guru is essential. Even big, big ācārya . . . even Kṛṣṇa, He accepted guru, Sandipani Muni. Lord Caitanya accepted guru, Īśvara Purī. They are perfect, but still, the ways They are showing because They are ācārya. Kṛṣṇa is teaching, taking the part of the ācārya, so He is also accepting, although the fact is as soon as went to, within a few days He learned everything. That is stated in our Kṛṣṇa book.
Within a few days He became expert warrior, expert magician, expert yogī, every . . . so many things, all arts. But He learned from a guru. He is perfect Himself, Kṛṣṇa. He is called Yogeśvara. He knows all the yoga process, but still, in order to teach us, because He is playing the part of a teacher, He shows us that you must learn from guru: "I am learning from guru."
So any science, you cannot learn it automatically by yourself. No. That is not. Then we shall create so many mental speculators, so many things. That will be not a science. Even all scientists, they accept a formula from an authority, "Law of gravitation." They accept it. Then their physical, so many things they discover. But accept one formula. Just like this formula is given by Sir Isaac Newton. So they accept guru.