When this gross body becomes useless or unworkable, then the subtle body carries me to another gross body. This is called transmigration of the soul. But we do not see the subtle body. Every one of us, we know that we . . . we have got mind, but we cannot see the mind. Neither we can see intelligence, neither I can see what is my ego. But they are existing. So it is not necessary that everything you have to see with your blunt eyes. The eyes, they are not perfect. Just like the other side of this hall is dark; I cannot see you, although I have got the eyes. So even though we have got eyes, it is very imperfect. It cannot see in all circumstances. Under certain circumstances we can see. Therefore we should not believe simply by seeing.
But one thing: although I cannot see you, you can hear me, or I can understand that you are hearing. The ears are stronger than the eyes. So things which is beyond our experience, we can hear about. Even though we cannot see, it does not mean there is no existence of things. The same example: even though I cannot see what is mind, what is intelligence, what is ego, but I can hear about it. Therefore perfect knowledge is acquired by hearing.
So we accept knowledge, perfect knowledge, by hearing. Another example, suppose a man is sleeping. At that time, if somebody is coming to kill him, he's sleeping, he does not know. But if some of his friend warns him, "My dear Mr. Such-and-such, somebody is coming to kill you. Wake up!" he can hear, and he can wake up and take precaution. Therefore, when our other senses cannot work, our ear is very strong. Therefore it is recommended that you try to hear from the authoritative person. That is also . . . educational system is also like that. Why do you come to university, school and college? To hear from an experienced professor. He knows, and you acquire the knowledge by hearing.
So the process of hearing is very important. So our this Kṛṣṇa consciousness movement is to propagate that, "You hear from the authority, Kṛṣṇa." Kṛṣṇa is the Supreme Personality of Godhead. It is accepted in the present age and in the past age. In the past age, great sages like Nārada, Vyāsa, Asita, Devala, very, very great stalwart scholars and sages, they accepted. In the middle age, say 1,500 years ago, all the ācāryas like Śaṅkarācārya, Rāmānujācārya, Madhvācārya, Nimbārka . . . practically, Indian Vedic civilization, it is still existing on the authority of these ācāryas. And it is recommended in the Bhagavad-gītā, ācāryopāsanam. If you want to learn factually things, then you should approach ācārya. Ācāryavān puruṣo veda (Chāndogya Upaniṣad 6.14.2), "One who has accepted ācārya, he knows things as they are." Ācāryavān puruṣo veda.