If you're not familiar, the theodicy is the question, how can evil exist if God is omnipotent, omnipresent, and omniscient... while being totally good. It seems that if He is everywhere, all powerful, and all knowing, and also all good, then He would prevent evil from ever occurring.
But Lewis demonstrates how this is false. He points out how God has made things in such a way as to give us truly free will. We can choose to follow Him and be kind to one another. Or we can choose to ignore Him and hurt each other very badly. If He forced us to do good, we would not be free.
And freedom is apparently very important to Him. He wants us to FREELY choose to love Him and do His will, not be forced to do it by the lack of any alternative.
Sometimes it's easy to wish that He DID force us to do His will. I mean, if I really want to do His will, and want His will done in the whole world... wouldn't I want Him to force His will on me and my life? When I pray "your kingdom come, your will be done on Earth as it is in Heaven", aren't I asking for just that?
As my good friend Amy says, yes and no. I AM asking for His will to be done. But I am NOT asking for Him to force His will on people who don't want it. I am, in fact, asking for Him to manifest His kingdom among those who WANT Him to be here in their lives, doing that amazing thing He does where He makes all things good, and all things good, and all manner of all things good (as Julian of Norwich said).
So come, Lord Jesus. Accomplish Your will in my life. In complete freedom, I ask for this with a free will. Thank You for allowing me to participate in Your work.