2.16 The unreal hath no being; there is non-being of the real; the truth about both has been seen by the knowers of the Truth (or the seers of the Essence).

2.16 Nasatah etc. And then, also following the common worldly practice [the Lord] says this : There is no [real] existence for what is non-existent i.e., the body [etc.], that is continuously perishing; for it is changing incessantly by stages. Again, never there is destruction for the ever existing Supreme Self, because of Its unchanging nature. So says the Veda too : 'Lo ! This Soul is of unchanging nature and [hence] is destructions' (the Br. U, IV, v. 14). Of These two : of what is existent and what is non-existent. Finality : the point of boundary where they come to an end. But is this permanent or transient which is perceived by persons who are prone to see the truth ? Having raised this doubt, [the Lord] says :

2.16. The unreal has no existence, and the real never ceases to be; the truth about both has indeed been perceived by the seers of the essence. Commentary: "The unreal has no existence" — The body did not exist before its birth, will not exist after death, and even in the present, it is ceasing to exist every moment. The meaning is that this body never exists in the form of a positive entity in any of the three times — past, future, or present. Therefore, it is unreal (asat). In the same way, this entire world also has no positive existence; it too is unreal. This body is but a small sample of the world. Therefore, through the changes in the body, one experiences the change in the entire world: that this world had no existence before, will have no existence afterwards, and even in the present, it is ceasing to exist. The entire world is constantly burning like wood in the fire of time. When wood burns, charcoal and ash remain, but the fire of time burns the world in such a unique way that nothing like charcoal or ash remains. It renders the world into sheer non-existence. Therefore, it is said that the unreal has no existence. "The real never ceases to be" — That which is the real entity never ceases to exist. That is, even when the body had not come into being, the indweller (dehi) existed; even when the body perishes, the indweller will remain; and even in the present, despite the changing body, the indweller remains exactly as it is within it. In the same way, even when the world had not manifested, the Supreme Reality (Paramatmatattva) existed; even when the world ceases to be, the Supreme Reality will remain; and even in the present, despite the changing world, the Supreme Reality remains exactly as it is within it. A profound point: We can see the world only once, not a second time. The reason is that the world is changing every moment. Therefore, an object as it was a moment before is not the same the next moment — just as when watching a cinema, the picture on the screen appears stable, but in reality, it changes every moment. Because the film on the machine moves rapidly, the change happens so swiftly that our eyes cannot catch it. An even more profound point is that, in truth, the world is not seen even once. The reason is that the instruments — body, senses, mind, intellect, etc. — through which we see and experience the world, are themselves part of the world. Therefore, in truth, the world is seen by the world itself. That which is entirely unrelated to the body-world is the Self (svarupa). From the standpoint of that Self, the world is never seen at all. The meaning is that in the Self, there is no perception of the world. The perception of the world occurs only in relation to the world. This proves that the Self has no relation whatsoever with the world. Secondly, without the aid of the world (body, senses, mind, intellect), the conscious Self cannot perform any action. This proves that action exists only in the world, not in the Self. The Self has no relation whatsoever with action. The nature of the world is action and objects. Since the Self has no relation with either action or objects, it is established that the entire world, including the body, senses, mind, and intellect, is non-existent. Only the Supreme Reality (Paramatmatattva) exists, which, while remaining unattached, illuminates and supports everything. "The truth about both has indeed been perceived by the seers of the essence" — The great beings who know the essence of both — the real and the unreal, the indweller and the body — have seen their essence, have extracted their quintessence: that only one Reality exists. The essence of the unreal object is also the Real, and the essence of the real object is also the Real. That is, the essence of both is one and the same Real; the essence of both is one and the same in its positive existence. Therefore, that which is known through the great beings who know the essence of both the real and the unreal is only one Reality. The existence that appears to belong to the unreal is also, in truth, that of the Real alone. It is only through the existence of the Real that the unreal appears to exist. This very Real is called 'Para Prakriti' (Gita 7.5), 'Kshetrajna' (Gita 13.12), 'Purusha' (Gita 13.19), and 'Aksha' (Gita 15.16). The unreal is called 'Apara Prakriti', 'Kshetra', 'Prakriti', and 'Kshara'. Arjuna is grieving over the bodies, thinking they will die if the war is fought. On this, the Lord says: Will they not die if the war is not fought? The unreal will surely die and is constantly dying. But that which is of the nature of the Real within it will never cease to be. Therefore, your grief is merely ignorance. In the eleventh verse, it is stated that the wise do not grieve for those who are dead or those who are alive. The twelfth and thirteenth verses describe the eternality of the indweller, using the word 'dhira' (the steady one). The fourteenth and fifteenth verses describe the impermanence of the world, and there too the word 'dhira' is used. Similarly, here (in the sixteenth verse) the discrimination between the real and the unreal is given, and in it the word 'tattvadarshi' (seer of the essence) appears. The purpose of using the terms 'pandita' (wise), 'dhira', and 'tattvadarshi' in these verses is to indicate that those who are discriminative and understanding do not grieve. If grief arises, they are not discriminative, not understanding. Connection: What the real and the unreal are is explained in the next two verses.