This week's Final Word comes from a friend of Einstein's who was similarly handy with equations:
"'The youth that was I', you may come to speak of him in the third person, indeed the protagonist of the novel you are reading is probably nearer to your heart, certainly more intensely alive and better known to you. Yet there has been no intermediate break, no death. And even if a skilled hypnotist succeeded in blotting out entirely all your earlier reminiscences, you would not find that he had killed you. In no case is there a loss of personal existence to deplore. Nor will there ever be."
As we received no correct answers to last week's Finl Word, which was David Marquand's The Unprincipled Society , next week's prize will be a £40 book token.