Gandalf really ‘died’ and was changed: for that seems to me the only real cheating, to represent anything that can be called ‘death’ as making no difference. ‘I am Gandalf the White, who has returned from death’. Probably he should rather have said to Wormtongue: ‘I have not passed through death (not fire and flood) to bandy crooked words with a serving-man’. And so on. I might say much more, but it would only be in (perhaps tedious) elucidation of the ‘mythological’ ideas in my mind; it would not, I fear, get rid of the fact that the return of Gandalf is as presented in this book a ‘defect’, and one that I was aware of, and probably did not work hard enough to mend. But Gandalf is not, of course, a human being (Man or Hobbit).
Letter 156, The Letters of JRR Tolkien