Why go on a Quest in the first place?

[Kuruharan]

I think that Gandalf aslo knew that Bilbo would find a ring possibly.

Well, yes and no. At one point in 'The Quest of Erebor' Gandalf says,
"Bilbo was meant to find the Ring, and not by its maker and you therefore were meant to bear it. And I might have added: and I was meant to guide you both to those points.
"To do that I used in my waking mind only such means as were allowed to me, doing what lay to my hand according to such reasons as I had. But what I knew in my heart, or knew before I stepped on these grey shores: that is another matter."

Then in another section,
"And suddenly I felt that I was indeed in hot earnest. This queer notion of mine was not a joke, it was right. It was desperately important that it [Bilbo's going along on the quest] should be carried out."

So I would say that Gandalf definitely knew that there was something else of vital significance that was going on besides securing for the Longbeards one of their former citadels. That he knew specifically that the Ring would be found, at least in his waking mind, I kind of doubt. Although, as he says, what he knew before he came to Middle Earth is a different matter.

And at the end he also says that he is still not telling everything that he knows. [img]smilies/smile.gif[/img]