Theology interests me. I think about it often. Although Walter has come to completely different conclusions, I do believe he gives this subject as much thought as I do, and I think that is rare.
He recently made a blog post to explicitly explain what he does believe. One thing that I think he was not clear on was "purpose". He didn't actually say that God gives his life purpose, but that seems to be what he means. I'd go as far as saying that he seems to think that it's so obvious that it goes without saying. What a strange concept, but he's not alone. This idea was first introduced to me years ago by another person who asked me, "How can your life have meaning without God?"
I didn't know how to answer that at the time. It's like asking, "How do you get home without a purple sharpie?" The ideas just aren't related. How could someone, anyone, who is not me, give my life meaning?
Let's assume that there is a God, and he not only cares about you, but has a specific purpose in mind for your life.
In what way does that give your life purpose? Lots of people have a purpose for you; your employer, your family, your government... Even the panhandler on the street has a purpose for you. Spoiler alert, it involves giving him money. None of these people can live your life for you. You might consider their opinions, but they are just that, their opinions.
You might suggest that God's plan must be followed to receive reward, or avoid punishment. What you need to do to survive is not the purpose of your life. We're talking about a means to an end.
You might suggest that God's plan should be followed, because it can be assumed that it is a good plan, or that you're obligated to follow it whether it is a good plan or not. Well, I don't know how you came to that conclusion, but that's still you giving your own life meaning based on God's suggestion. His purpose is just one more purpose that you had to decide among.
And finally, even assuming that all of that is true:
1. There is a God.
2. He has a purpose for your life.
3. Him deciding that can, somehow, give purpose to someone else's life.
Wouldn't that need to be explicitly communicated to you? How can someone give you a purpose without actually giving you the purpose? 'God has a plan for you... try to guess what it is.' That's like saying that there's this perfect map of the area, but no one has ever seen it, and no one ever will see it. Okay, well, then there's not a map. We'll have to make our own.