The Rev Sam says here:
"What does it mean to believe in God? Specifically, what does it mean for a Christian to believe in God? As I understand it, the essential element is about meaning or purpose - to believe in God is to believe that life is meaningful, is purposeful, and this meaning is by definition independent of personal choice or preference, it is something that stands outside of our desires and it is something to which we need to conform in order to flourish."
That may be true. But I just want to point out that having an objective, externally given purpose does not necessarily give life a meaning. Even if it does help us flourish.
In his book Atheism - A Very Short Introduction, Julian Baggini has a nice analogy, which I now develop somewhat here.
Suppose it turns out that we do have a purpose. Human beings are being bred on Earth by aliens. And for a purpose too. To clean their toilets. They are coming next week to pick us up and take us to where we can fulfill our true purpose - to forever toil, cleaning the enormous toilets of the giant three-bummed aliens of Avatar! It's a purpose for which we are extremely well adapted. Indeed, when we start doing it, we find everything about us starts to make sense. Our bodies just fit perfectly into the role. Indeed, we find we gain a profound sense of satisfaction from cleaning their giant bogs - for we are designed find the smell their excrement extraordinarily addictive. We never want to do anything else! We flourish and finally feel "fulfilled" in a way we have never felt before!
You know that "hole" we all feel deep down inside - that yearning for we-know-not-what? - it's finally fulfilled... by alien poo!
Would this make our lives meaningful?
I am reminded of the cow-like beast in Douglas Adam's The Restaurant at the End of The Universe - a being that is bred to want to be eaten "Which bit of me what you like to eat, sir? Perhaps my rump, chargrilled?" - whose death and consumption is what it's designed for, and what it desires above all else. Is this creatures' life meaningful? Does having an externally given purpose make it meaningful?
The question is, why should the discovery that we were made by God for a purpose - to love and worship him - make our lives meaningful? Theists almost always just assume this would make our lives meaningful - but it's not at all clear why it should.
They really need to explain why it would. Can they? I am guessing they can't. But then it turns out they no more have an account of what makes life meaningful than does the atheist.
Personally, I'd find it pretty dreadful to discover my purpose is endlessly to adore, worship and obey someone that designed me - be it an alien or God. Certainly, the discovery wouldn't make me feel that my life was now more meaningful. If anything, it'd make me feel it was now rather less meaningful.
POSTSCRIPT: Incidentally, the assumption that having a God given purpose is the (only) thing that can make our lives meaningful is very typical of the kind of lazy thinking theists typically get away with. How many of them have ever subjected this assumption to critical scrutiny, I wonder? Very, very few, I'd guess. Yet they are typically very keen on subjecting atheist and humanist views on meaning to the minutest critical scrutiny.