Bhava means to grow; means . . . grow means which has taken birth. That requires grow. In the material world, there are six kinds of changes: first of all birth, then grow, then stay for some time, then producing some by-product, then diminishing, dwindling, and then vanish. These are the six kinds of changes. Just like this body: It has taken birth at a certain date, and it has grown, that the child is growing. And growing, it will stay; not immediately vanish. It will stay. And while staying, it will create some by-product. From this body, so many sons and daughters will come, by-product. Even tree, they produce also. Everyone. Then it becomes old, no more strength, and when it is very old, finish. These are called ṣaḍ-vikāra. That is on account of this body.
So after finishing this body, then I am not finished; I am there. I am, this gross body, finished, but I am within this subtle body—mind, intelligence and ego. The subtle body carries me to another gross body. These so-called scientists, medical men, they cannot see the subtle body, although one has to accept. Just like I have got mind; you have got mind—but I cannot see your mind; you cannot see my mind. I have got intelligence, you have got intelligence. Everyone knows. But you cannot see my intelligence, I cannot see your intelligence. They are very subtle. So, and beyond that, the spirit soul is still subtle, so minute quantity. So what these material scientists will see? They cannot see the mind, intelligence, ego, and what to speak of the soul. Therefore they say, "This body is everything, and there is nothing more." But actually that is not the fact. The fact is that the spirit soul is very, very small. Keśāgra-śata-bhāgasya śatadhā kalpitasya ca (Śvetāśvatara Upaniṣad 5.9). Keśāgra, the tip of the hair, agra-bhāga, front portion, front portion, śata-bhāgasya, you divide into . . . can you do it? Take one hair and divide into hundred parts? No, that is not possible. But if . . . the direction is there. If you can, you can do it. Śata-bhāgasya. Then again take one part of that śata-bhāga, one hundredth part, again make it hundred parts.
So it is not possible; impossible by the so-called scientists. But how to learn? Then you have to learn from the authority, "It is like this," that much. It is not under your experimental knowledge. That is not possible. Because your knowledge is so imperfect, you cannot deal with these things. But these rascals, they think . . . because they cannot deal with these things, they think that the matter is the cause of life. That's all—matter, material. But that is . . . they have not been able to do so. Take matter in the laboratory, chemicals, and produce a small insect with hands and legs and eyes. We see every night, a small, very, very small, but still, it has got hands, legs and everything, eyes. Otherwise how they are coming to the light? Very small.