"Without a flow of power to my brain, I would cease functioning," Daneel confirms, "and yes, it would be permanent. Another positronic brain might be fitted into my body, but it would not be... myself. There are too many variables involved; as no two organic brains might be identical, neither or no two positronic brains. Even if it could have my memories, the new robot would not be myself. It would mean my... death, if you prefer."

Not an easy word for him to use regarding himself.

"As it is, I have been prevented from taking such an action."