Kṛṣṇa says, yat taj jñānam. Kṣetra-kṣetrajñayor yat taj-jñānaṁ mataṁ mama. Kṛṣṇa is giving that one should know what he is and one should know what is his body; then he is in knowledge. The matter cannot understand this. The dogs, cats, cannot understand this. But a human being can understand this. Bhagavad-gītā is meant for the human being, not for the cats and dogs. Therefore, the human society should take care of this knowledge. Then his life will be successful.
So it is very simple thing, that kṣetra . . . as I have given the example, that I am sitting on this floor. The floor is different identity from me. No sane man will say that, "I am this floor" or "I am this room." Nobody will say. It is my room, my floor. Similarly, this body, we say: "my," "my finger," "my head," "my leg." Nobody says that "I leg," "I finger," "I head." No. This is knowledge. Don't identify yourself with this body. This is knowledge. This is beginning of spiritual life. The cats and dogs, they cannot understand. The cat cannot understand that he's not body. The dog cannot understand that he is not body. It is the human being who can understand. So if in the human life one does not try to understand this simple knowledge, then he remains like cats or dogs. He's no better than cats and dogs.
This is one point: that I am not this body; I am not this material world. I am a spiritual identity, part and parcel of God. Qualitatively we are one. As God is spirit, so I am also spirit. But His body is very big, gigantic, the universal body, which Kṛṣṇa showed to Arjuna, the virāṭa-rūpa. But my body is not gigantic. It is small. Maybe we call the elephant's body gigantic or similar other animal's body, but still God's body is still more gigantic. You cannot compare. Eleventh Chapter of the Bhagavad-gītā you'll know how gigantic body has Kṛṣṇa. So as I have got this body but my spiritual identity is very small, if we study in this way, it is very easy to understand what is God, what I am, what is this world.
Just like I am . . . I am not this body; I am within the body. Dehino 'smin yathā dehe (BG 2.13). I am the proprietor of the body. But what is my magnitude? Keśāgra-śata-bhāgasya śatadhā kalpitasya ca (Śvetāśvatara Upaniṣad 5.9). You just take the top of the hair and divide it into ten thousand parts. That one part is your identity. So in these material ideas, we cannot understand that such a small particle, smaller than the atom, has got so power. Therefore, because it is so small, these so-called rascal scientist, they cannot find it, where it is; therefore say, "There is no soul." The rascals will not admit their inefficiency to know, and still they will say, "No soul." And if there is no soul, then how it is working? They have no even common sense.