There are three stages. First stages of understanding is direct perception, by senses. Indriyāṇi parāṇy āhuḥ (BG 3.42), in the Bhagavad-gītā you'll find. Here, from the material platform, our source of knowledge is direct perception. That is crude, pratyakṣa. It is called pratyakṣa. That is crude knowledge, direct perception. Just like I am seeing the sun. I am getting some idea of the sun, but that is not the perfect idea, although I am seeing it daily. I am seeing just like a disc, but it is very, very big.
So my direct perception cannot give me perfect knowledge. The first . . . besides that, at our present stage, material condition, we are imperfect because we commit mistake. By direct seeing the sun, I am thinking that it is just like a disc. Then we are illusioned. We, sometimes we accept something for something. Then, with this imperfect knowledge, we try to become teacher. That is cheating. And at the end, our senses are imperfect. So with so many imperfectness, how we can get perfect knowledge? What is your answer?
Professor: I have no answer.
Prabhupāda: Yes. Therefore, our speculative knowledge, intellectual platform, is not helpful. We must receive knowledge from superior source, perfect source. That knowledge is perfect. Just like we give generally this example, that to find out who is my father, my search out, research, will not help me; but if my mother says: "Here is your father," that is perfect knowledge, because she's authority. Therefore, for perfect knowledge we have to take it from the perfect authority, not by our speculative intellectual gymnasium. No. That will not help. Because our intellectual jurisdiction is very limited. That is Vedic process. Vedic process is not to acquire knowledge by ascending process, inductive process. Vedic knowledge is to receive knowledge by descending process, knowledge coming from authority.
That, that you will find in the Bhagavad-gītā, Fourth Chapter: evaṁ paramparā prāptam imaṁ rājarṣayo viduḥ (BG 4.2). Knowledge has to be received . . . just like a child receives knowledge. He is inquisitive: "Mother, what is this? Father, what is this?" And mother informs him, "My dear child, this is this, this is this." So he is acquiring knowledge by descending process. And if the child wants to get knowledge independently, that is not knowledge. He'll touch the fire. Mother: "Don't touch, don't touch, my dear child!" But he does not know. He's thinking the fire as something eatable.
So by the Vedic process, this experimental knowledge is no useful. Yes. The Vedic injunction is, tad-vijñānārthaṁ sa gurum evābhigacchet: (MU 1.2.12): "In order to receive perfect knowledge, you must approach the guru." Guru means who has the perfect knowledge. So you cannot independently get perfect knowledge, intellectual. That will remain always imperfect. So intellectually, how you can conceive about God, who is unlimited, beyond your sense perception? We cannot know even ordinary material things, how great the sun is, how this universe is. We have imperfect knowledge.