Verse 2.13: (Page 22 in notes): Krishna tells Arjuna that Bhīsma sarīra will go but Bhīsma Ātma will not go. So why are you grieving?
Few thoughts crossed my mind regarding this statement:
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1) In reply, Arjuna might as well say: "I don't even want to destroy the body of Bhishma".
(Body "belongs"to Bhishma (Atma). But we don't destroy "belongings" of others, especially of our dear ones, right? For example: I don't like to harm/destroy someone's "belongings" - like car, toy etc)
2) I am wondering what would have been Krishna's answer, if Arjuna said so.
let us analyse this in opposite way. Is it ok to take somebody’s property or kill somebody because everything is not real. This is argument many put forth. most important character of jnani is - No desire for fruits. He performs action in accordance with divine will. he will not be able to treat anybody as other than him. So his actions will always be in line with dharma. Why would somebody kill some one or rob. When he treats that person as other than him, so he assumes that whatever he gets out of it is real. So as long as he believes there in other than him. His killing is also real. So he is responsible for his actions. in conclusion, any action performed with desire for fruits and performed with sense of “otherness “ will incurs result and the doer is responsible
Ramana Maharshi was once asked- ‘How should we treat others?’
He answered- ‘there are no others.’
For a jnani, once he identifies himself with Brahman, there are no others... the whole play of life and death becomes literally inconsequential. With that perspective, he is not harming/ destroying any one. This is Sri Krishna’s first and strongest level of argument to convince Arjuna not to grieve.
Further, He persuades Arjuna to fight by explaining the next levels: of dharmic duty and world views.