The Powers of the Istari

[obloquy]

For the sake of keeping all the relevant text in the same thread, I'm resurrecting this in order to post a bit more relating to the note mentioned in gorthaur_cruel's post.

First, another couple of letters from the same time period tell us that Sauron was a Maia originally attached to Melkor, rather than Aule. This is an aspect of Sauron's origin that we all know was revised after the cited letter of 1956.

Secondly, a portion of letter 246 of 1963 is doubly pertinent to this discussion:

Of the others only Gandalf might be expected to master [Sauron]--being an emissary of the Powers and a creature of the same order, an immortal spirit taking a visible physical form.

Not only are Gandalf and Sauron "of the same order" here, but Gandalf "might be expected to master Sauron."