23. Consciousness, which is the symptom of the soul, can be perceived by material instruments, but the soul itself cannot be contacted by any material object. This is so only because the soul is divine, and hence beyond the interactions of material objects. Shree Krishna expresses this vividly by saying that wind cannot wither the soul, nor can water moisten it or fire burn it.
24. The point about immortality is again being driven home here. For the teacher to merely impart perfect knowledge is not enough; for that knowledge to be useful, it must sink deep into the heart of the student. Hence a skillful teacher often repeats a point previously made. In Sanskrit literature, this is called punarukti, or "repetition." Shree Krishna has often used punarukti, as a tool in the Bhagavad Gita for stressing the important spiritual principles to ensure that they are grasped deeply by his student.
25. Our eyes, made from material energy, can see only material objects. The soul, being divine and beyond the realm of material energy, is invisible to our eyes. Scientists have conducted experiments to perceive its presence. They put a dying person into a glass case and sealed the case, to see whether the departure of the soul would crack the glass. However, the soul left the body without the glass box getting cracked. Being subtle, the soul did not need physical space for its movement.
Being subtler than the material energy, the soul is also inconceivable to our intellect. The Kaṭhopaniṣhad says:
"Beyond the senses are the objects of the senses; subtler than the objects of the senses is the mind. Beyond the mind is the intellect; and subtler than the intellect is the soul." The material intellect can only comprehend material concepts, but can never reach the divine soul by the power of its contemplation. As a result, knowledge of the self requires external sources, which are the scriptures and the Guru.
26. Shree Krishna uses the word atha to indicate that Arjun may want to believe the other explanations that exist about the nature of the self. This verse needs to be understood in the context of the philosophical streams existing in India and their divergent understandings about the nature of self. Indian philosophy has historically comprised of twelve schools of thought. Six of these accept the authority of the Vedas, and hence they are called Āstik Darśhans. These are Mīmānsā, Vedānt, Nyāya, Vaiśheṣhik, Sānkhya, and Yog. Within each of these are more branches—for example, the Vedānt school of thought is further divided into six schools—Adavita vāda, Dwaita vāda, Viśhiṣhṭādvaita vāda, Viśhuddhadvaita vāda, Dwaitādvaita vāda, and Achintya-bhedābheda vāda. Each of these has further branches, for example, Advaita vāda is subdivided into Dṛiṣhṭi-sṛiṣhṭi vāda, Avachchheda vāda, Bimba-pratibimba vāda, Vivarta vāda, Ajāta vāda, etc. We will not go into the details of these schools here. Let it suffice for now to know that all these schools of thought accept the Vedas as the authority of reference. Accordingly, they all accept the eternal, unchangeable soul as the self.
The remaining six schools of Indian philosophy do not accept the authority of the Vedas. These are Chārvāk vāda, the four Buddhist schools (Yogāchār vāda, Mādhyamik vāda, Vaibhāśhik vāda, and Sautāntrik vāda), and Jainism. Each of these has its own explanation for the nature of the self. Chārvāka vāda states that the body itself comprises the self, and consciousness is merely a product of the conglomeration of its constituents. Jainism states that the soul is the same size as the body, and hence, it is subject to change from birth to birth. The Buddhist schools of thought do not accept the existence of a permanent soul, and instead maintain that there is a stream of renewed animation from lifetime to lifetime, which ensures continuity of the individual.
It seems that at the time of Shree Krishna too, versions of the Buddhist philosophy of renewed animation and non-permanence of the soul existed. Hence he is explaining that even if Arjun subscribes to this philosophy of renewed animation of the self from life to life, there is still no reason to lament. Why should one not lament? This is now explained in the next verse.
27. In English language, there is a popular idiom, "as sure as death." Benjamin Franklin said: "The only things certain in life are death and taxes." The most certain thing in life is that we will meet with death one day. Psychologists categorize the fear of death as the biggest fear in life. In Patanjali's Yog Darśhan too, abhiniveśh, or the instinctive urge to survive at all costs, is mentioned as a trait of the material intellect. But for one who has taken birth, death is inevitable. So when something is inevitable, why lament over it?
The Mahabharat relates an incident regarding this. During the period of their exile in the forest, one day while wandering the five Pandavas were thirsty and came across a well. Yudhishthir asked Bheem to go and fetch water for all of them. When Bheem reached the well, a yakṣha (powerful spirit) began speaking from inside the well, "I will only let you take the water if you first answer my questions." Bheem paid no heed and proceeded to draw water. The yakṣha pulled him in. After some time when Bheem did not return, a concerned Yudhishthir sent Arjun to see what was happening and fetch water. When Arjun reached the well, the yakṣha asked him too, "I have already seized your brother. Do not attempt to draw the water unless you can answer all my questions correctly." Arjun also paid no heed, and the yakṣha pulled him into the well. The other brothers, Nakul and Sahadev, followed him, but met with the same fate. Finally, Yudhishthir himself came to the well. Once again, the yakṣha said, "Answer my questions if you want to drink water from the well, or I will pull you in, just as I have done to your four brothers." Yudhisthir agreed to answer the questions. The yakṣha was actually the celestial God of death, Yamraj, in disguise. He asked sixty questions, each of which was answered perfectly by Yudhishthir. One of these questions was: kim āśhcharyaṁ? "What is the most surprising thing in this world?" Yudhisthir replied:
"At every moment people are dying. Those who are alive are witnessing this phenomenon, and yet they do not think that one day they will also have to die. What can be more astonishing than this?" Shree Krishna explains in this verse that life is inescapably a dead end, and so a wise person does not lament over the inevitable.
28. Shree Krishna dispelled the cause of lamentation in respect to the soul, and in respect to the body. Now he includes both in this verse. Sage Narad instructed Yudhishthir along similar lines, in Śhrīmad Bhāgavatam:
"Whether you consider the personality to be an eternal soul or to be a temporary body, or even if you accept it as an inconceivable mixture of soul and body, you should not lament in any way. The cause for lamentation is only attachment that arises out of illusion."
In the material realm, each individual soul is bound by three bodies—gross body, subtle body, causal body.
Gross body: Consists of the five gross elements of nature—earth, water, fire, air, and space.
Subtle body: Consists of eighteen elements—five life-airs, five working senses, five knowledge senses, mind, intellect, and ego.
Causal body: Consists of the account of karmas from endless past lives, including the sanskārs (tendencies) carried forward from previous lives.
At the time of death, the soul discards its gross body, and departs with the subtle and causal bodies. God again gives the soul another gross body according to its subtle and causal bodies, and sends the soul into a suitable mother's womb for the purpose. After the soul gives up one gross body, there is a transitional phase before it receives a new gross body. This could be a few seconds in duration or a few years long. So before birth, the soul existed with the unmanifest subtle and causal bodies. After death, it still exists in the unmanifest state. It only becomes manifest in the middle. So death is no reason for grief.