If you have no sufficient knowledge on a subject matter and if you want to enlighten others with your speaking, that is cheating. Because you have no sufficient knowledge, why you are speaking to others? That is cheating. He is posing that, "I know," but he does not know. This is cheating. Imperfectness of senses. They are declaring that "We are studying the planetary system by," what is called, "telescope." But who has manufactured this telescope? You have manufactured, or your brother has manufactured. But he has got imperfect senses. How the telescope will be perfect?
So this is going on. They are simply cheating public. They have no sufficient knowledge, still they are trying to speak of some subject of which they have no sufficient knowledge. Besides that, the scientist . . . one scientist proposes, theorizes something today, and another scientist makes this proposition, this theory, null and void and he speaks something else. That is also due to the imperfect of senses.
So that is called mistake or illusion. Mistake means calculation, mathematical calculation, "Two plus two equal to four"; but sometimes by mistake we may put "three" or "five." That is called mistake. And illusion, to accept something for something. Just like we are accepting, when somebody inquires, "Who are you?" you just give identification of your body: "I am such and such. I am an American. I am born of such father and mother, by a . . ." But this body is not yourself. You are spirit soul. Therefore it is called illusion. And because we are struggling on the platform of illusion, there is mistake, there is cheating, and the senses are imperfect. This is the position.
Therefore, the so-called modern scientific world, advanced, they do not know what is the actual living force within this body which is moving this body. So long the soul or the living force is within this body, it is moving. As soon as the spirit soul is out of the body, it is . . . we call it is dead.
So we have got medical science for this body, we have got psychology for the mind—everything we've got—but where is the science of the soul, which is moving the body and the mind? Where is that science? Is there any such science? You are all students, I think. To understand what is the basic principle of moving this body and the mind, is there any department of knowledge in the universities all over the world to understand this science? Is there any?
Then where is your knowledge? Somebody is accepting the mind as the self, and somebody is accepting the . . . this gross body as the self. They do not know that both the body and the mind, both of them are material. And the force, or the entity, which is moving this body and mind, that is spirit. So they have no knowledge.
So that knowledge is being imparted by the Supreme Personality of Godhead, dehino 'smin yathā dehe (BG 2.13). Dehī, the soul, the proprietor of the body . . . just like you are the proprietor of your body. When I touch your finger, if I ask even a small child, "What is this?" he will immediately say: "My finger." He'll never say: "I finger." "My finger." Just try to understand. When any part of your body I touch, if I ask, "What is this?" you will say: "This is my hand," "This is my leg," "This is my nose," "This is my . . ." Everywhere you will say: "my." But nobody knows what is that "I." Nobody knows.
But the "I" is there. Otherwise, how you say "my"? When the "I" is not there, we cannot say "my." When you are sitting here, so long you are there, you claim, "This is my shirt," "This is my coat," "This is my book," "This is my friend," "This is my wife," "This is my husband." But when a man is dead, ask him; no reply "I" or "my."
So this human life especially meant for understanding what is that "I." In the bodily concept of life, just like animal, they fight with some piece of flesh, two dogs fighting. The one dog is claiming, "It is my flesh"; another dog claiming, "My flesh." But they cannot understand what is that "I." They are claiming "my," but they have no understanding of "I." Therefore, if a human being simply claims "my"—"my country," "my society," "my wife," "my husband," "my body," "my dress," "my furniture," "my home"—where is "I"? This they do not think. They have no knowledge.
In the school, college, university, there is no such knowledge what is that "I." Simply "My." So this Kṛṣṇa consciousness movement is meant for educating, educate people what is that "I." Everyone is engrossed with things, illusorily thinking "my," but he has no identification what is that "I."
So Kṛṣṇa is giving instruction in the Bhagavad-gītā that "I" within the body is there. And the "I," or the spirit soul, that is changing the body. Dehino 'smin yathā dehe (BG 2.13). How changing? Just like a baby. A baby grows to become a child, a child grows to become a youth. Boy, a boy grows to become youth, a youth grows to become old man. So this change is not of that "I." It is a change of the outward body, which is known as shirt and coat. Just like you have coat and you have shirt also. But when the coat is not useful, you cannot use anymore, you throw away the coat, you keep your shirt, then again you find out another coat.
Similarly, the living entity, the living force within this coat, body and mind, there is the soul. The soul is changing one coat to another. Similarly, tathā dehāntara-prāptiḥ (BG 2.13). Dehāntara means accepting another body. The soul is changing dresses: sometimes this human form of body, sometimes the cat's form of body, dog's form of body, tree's form of body, beast form of body, demigod form of body, in this way. The same soul. Tathā dehāntara-prāptir dhīras tatra na muhyati (BG 2.13).
So try to understand this. This is the basic principle of spiritual knowledge. If you understand yourself, then you understand God very easily. Because we are part and parcel of God.