The soul is eternal and never slain; act in Krishna consciousness to transcend karmic bondage.Listen — Srila Prabhupada Uvaca
Bhagavad-gītā 2.19–25 — October 14, 1968, Seattle 681014BG-SEATTLE [69:02 Minutes] Viṣṇujana: "He who thinks that the living entity is the slayer or that the entity is slain does not understand. One who is in knowledge knows that the self slays not nor is slain." [Bg. 2.19] [He who thinks that the living entity is the slayer or that he is slain, does not understand. One who is in knowledge knows that the self slays not nor is slain.] Purport: "When an embodied being is hurt by fatal weapons, it is to be known that the living entity within the body is not killed. The spirit soul is so small that it is impossible to kill him by any material weapon.
Nor is the living entity killable in any case, because of his spiritual constitution. What is killed or is supposed to be killed is the body only. This, however, does not at all encourage killing of the body. The Vedic injunction is mā hiṁsyāt sarvā bhūtāni [Bg. 9.4]: [By Me, in My unmanifested form, this entire universe is pervaded. All beings are in Me, but I am not in them.] Never commit offenses of violence to anyone.
The understanding that a living entity is not killed does not encourage animal slaughter. Killing the body of anyone without authority is abominable, and it is punishable by the law of the state as well as by the law of the Lord." Prabhupāda: [aside:] Where he is going? Viṣṇujana: "Arjuna, however, is being engaged in killing for the principle of religion, and not whimsically." Prabhupāda: Hmm. Viṣṇujana: This is verse twenty: "For the soul there is never birth or death. Nor, having once been, does he ever cease to be.
He is unborn, eternal and ever-existing, undying and primeval. He is not..." Prabhupāda: These are the statements of Kṛṣṇa. Now the constitution of the soul... So far materialists are concerned, they cannot even find out where is the soul.
Therefore there are so many theories. Actually, they cannot find out where the soul is situated because material senses cannot approach. The measurement of the soul is stated in the Vedic literature as one ten-thousandth part of the tip of the hair. So there is no possibility of understanding what is soul by material scientist. The only process is to take it from higher authorities like Kṛṣṇa. Kṛṣṇa here gives definition of the soul.
So we have to accept it. And not blindly accept it, but try to understand as far as possible with your arguments and reason. But this is the actual fact. Fact.
What is that statement? The soul, definition of soul, Kṛṣṇa is giving? Viṣṇujana: "Only the material body of the indestructible, immeasurable and eternal living entity is subject to destruction." [Bg. 2.18] [Only the material body of the indestructible, immeasurable and eternal living entity is subject to destruction; therefore, fight, O descendant of Bharata.] "He who thinks that the living entity is the slayer or that the entity is slain does not understand. One who is in knowledge knows that the self slays not nor is slain." [Bg. 2.19] [He who thinks that the living entity is the slayer or that he is slain, does not understand. One who is in knowledge knows that the self slays not nor is slain.] Prabhupāda: Then?