Eru letting Melkor go..

I'll go ahead and bite, and put a few questions out there...

I think that deep with in us, we all long for a sort of utopia...that perfect place with no tears, pain, fear. Just beauty, love...etc. Which is a bigger topic than just Tolkien.

Without darkness, could we enjoy, understand, appreciate the light?

Without the storm, would the calm mean as much?

Without evil, would "good" be so, well, good?

Perhaps Eru, in his wisdom, knew that in order for creation to have deeper freedom, there was need for Melkor and the evil that he brought. Creation was suddenly given a choice...although it sounds strange...they were not "enslaved" to good. They were able to chose Eru and the way of the Valar, or Darkness and the way of Melkor.

?