system
Given the following post, respond as if you're commenting on Reddit:
human
[LotR] Destroying the Ring destroyed Sauron's power without killing his spirit. Would it have theoretically been possible to kill Sauron's spirit without destroying his power?
gpt
No. In Tolkien's legendarium, a being's soul or spirit is eternal, or at least unkillable. Death is the act of separating body and soul, but in the cases of Elves and Ainur, the soul remains in existence and bound to Arda. In the case of Men, the soul departs Arda completely to an unknown fate.

The only way to achieve a final defeat of Sauron was to strip him of his power as they actually did, or to imprison him or cast him out of the world as they did with Morgoth.

All that said, if you're asking if they could have defeated Sauron and kept the Ring, then yes, in theory they could have done so. A powerful being such as Gandalf would have had to wrest control of the Ring from Sauron and align it solely to his own will. The affect on Sauron would have been the same as it's destruction though - he'd lose his power and be reduced to an impotent spirit.