How do realized ones know that cosmic consciousness is eternal and remains after the death of the body?

According to Osho, realized ones don’t speculate about survival; they abide wholly in the present. Their certainty is immediate, like knowing a headache: they directly experience themselves not as the perishable body but as vast inner space. Space cannot die; only the ‘walls’ (the body) fall. Thus eternity is known through direct realization, not belief or promise.