So we have to take this knowledge from authority. Here is Kṛṣṇa speaking. He's authority. We accept Kṛṣṇa: the Supreme Personality of Godhead. His knowledge is perfect. He knows past, present, and future. Therefore, He is teaching Arjuna, "My dear Arjuna, the spirit soul within this body is eternal." That's a fact. Just like I can understand, I was in the past, I am in present, so I must be in the future. These are three phases of time, past, present, and future. In another place, we read in this Bhagavad-gītā, na jāyate na mriyate vā kadācit. The living entity is never born; neither it dies. Na jāyate means he never takes birth. Na jāyate na mriyate, it never dies. Nityaṁ śāśvato 'yam, na hanyate hanyamāne śarīre (BG 2.20). It is eternal, śāśvata, existing forever. Na hanyate hanyamāne śarīre (BG 2.20). By annihilation of this body, the soul does not die. Because... This is also confirmed in the Upaniṣads, Vedas: nityo nityānāṁ cetanaś cetanānām eko bahūnāṁ vidadhāti kāmān. The God is also eternal, and we are also eternal. We are part and parcels of God. Just like gold and fragments of gold; both of them are gold. Although I am fragment, a particle of gold or the spirit, still, I am spirit. So we get this information that both God and we, living entities, we are eternal. Nityo nityānām, nitya means eternal.
So two words are there. One is singular number, nitya, eternal, and the other is plural number, nityānām. So we are plural number. Plural number eternals. We do not know what is the numerical strength of the living entities. They are described as asaṅkhya. Asaṅkhya means without any counting capacity. Millions and trillions. Then what is the difference between this singular number and the plural number? The plural number is dependent on the singular number. Eko bahūnāṁ vidadhāti kāmān. The singular number eternal is giving all the necessities of life to the plural number, we living entities. That's a fact, we can examine by our intelligence. Out of 8,400,000 different forms of life, we civilized human beings are very few. But others, their number is very great. Just like in the water. Jalajā nava-lakṣāṇi. There are 900,000 species of life within the water. Sthāvarā lakṣa-viṁśati; and 2,000,000 different forms of life in the vegetable kingdom, plants and trees. Jalajā nava-lakṣāṇi sthāvarā lakṣa-viṁśati, kṛmayo rudra-saṅkhyayaḥ. And the insects, they are 110,000 different species of form. Kṛmayo rudra-saṅkhyayaḥ pakṣīṇāṁ daśa-lakṣaṇam. And birds, they are 1,000,000 species of forms. Then beasts, paśavas triṁśa-lakṣāṇi, 3,000,000 types of animals, four-legged. And catur-lakṣāṇi mānuṣaḥ, and the human being the forms are 400,000. Out of them, most of them are uncivilized.