The subtle body is made of mind, intelligence and ego. Just like we forget about this body at night, and the subtle body works. We dream. We are taken away from our home, from our bed, to some other place, and completely forget this body. And when the sleep is over, we forget about the dream and we become attached to this gross body. This is going on, in our daily experience. So I am the observer. I am sometimes in this gross body and sometimes in the subtle body. But it is changing. But I am the observer. Therefore the inquiry should be that, "What is my position? At night I forget my gross body, and during daytime I forget my subtle body. Then what is my real body?" These are the questions.
So this is culture. You may do your business. Just like Arjuna: Arjuna was doing his business. He was a fighter, kṣatriya, but he did not forget his culture, hearing Gītā from the master. That is culture. If you simply do business and do not cultivate your spiritual life, then it is useless waste of time. Śrama eva hi kevalam (SB 1.2.8), the śāstra says. Svanuṣṭhitasya dharmasya saṁsiddhir hari-toṣaṇam (SB 1.2.13). Ataḥ pumbhir dvija-śreṣṭhā varṇāśrama-vibhāgaśaḥ.
So our Kṛṣṇa consciousness movement is being spread up that, "Do not forget your cultural life." We do not say that you stop your business and become a sannyāsī like me and give up everything. We do not say, neither Kṛṣṇa said that. Kṛṣṇa never said Arjuna that, "You give up your business." "You are kṣatriya. You are declining fighting. Oh, it is very abominable. You should not say like that. You must fight." That was Kṛṣṇa's instruction. So similarly, we Kṛṣṇa conscious people, we are also advising everyone that, "You do not give up your business."
Caitanya Mahāprabhu said also: sthāne sthitāḥ śruti-gatāṁ tanu-vāṅ-manobhiḥ (SB 10.14.3). Caitanya Mahāprabhu never said that "You give up your position." Position giving up is not very difficult. But to cultivate spiritual knowledge, that is required. Tasyaiva hetoḥ prayateta kovidaḥ na labhyate yad bhramatam upary adhaḥ (SB 1.5.18).
Now the animal life, there is no cultivation of spiritual life. That is not possible. The animal cannot cultivate this knowledge. The human being, if they do not cultivate spiritual knowledge, they're exactly like animals. Dharmeṇa hīna paśubhiḥ samānāḥ. So we should be very conscious about our eternal existence. Na hanyate hanyamāne śarīre (BG 2.20). Nityaḥ śāśvato 'yam. We, spirit soul, we are eternal. We are not going to die after the annihilation of this body. This is the cultivation of knowledge. This is called brahma-jijñāsā: to know about one's self.