system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If Gandalf knew Bilbo has the ring, why did he let him keep it?
gpt
He didn't know it was The One Ring - it was thought to be destroyed. In The Hobbit the ring was nothing special (other than the invisibility), and in the Lord of the Rings books it took Gandalf 17 years from Bilbo's farewell party to discover that it was in fact Sauron's ring.