Cartesian rethinking - a circle unwound

Lately I read a book called 'Maya', by Jostein Gaarder. He's a Norwegian author, and I've read two of his other books called 'Sophie's World' and 'The Solitaire Mystery' respectively. He usually puts in pieces of philosophy in his stories, and it makes for quite good reading.
With this book he appears to hold a very firm 'evolutionary' and atheistic standpoint (or at least the characters do), but that's not quite what I want to observe today. No, I want to do a little bit of my own philosophy, which has probably been done before, but if it has, I'm not aware of it.
So, we've heard on inumerable occasions Descartes' legendary premise Cogito Ergo Sum, 'I think therefore I am'. Now many people criticise this as flawed logic, that even if one is, it doesnt necessarily depend on them thinking, or some other convuluted twisting of thoughts and the merry-go-round usage of reasonable logic.
Today I was thinking on the issue. (OK go easy on me - do I be just because I was thinking?) I came up with something which struck me as more important, and I couldnt see anything wrong with it logically, but it came largely from being exposed to the perspectives portrayed in the aforementioned book. The philosophical premise that came to mind was:

I am, therefore Why am I?

Now I pondered how that would come across in other languages, and realised from my limited perspective on world languages (including French and Arabic), it struck me that in both French and Arabic (and probably Spanish too - dont know about German) 'Why' translates more like 'for what'. (In French pourquoi, and in Arabic limadha.) So another possibility for the statement is:

I am, therefore For what am I?

I personally (being the one who is here!) think that this is a much more important question for humanity, and cuts through any unnecessary existentialisms, getting right to the question which should be asked every time we notice we are. That question is 'What is the purpose of life?'.

Lets agree that we exist, in some way or other, cos there's a bit of communication between us. I could very well be talking to myself, but I believe the statement is still relevent. I exist, so why do I exist? Dont you feel that's something we should ask ourselves?

The answer of course, is simple. Or maybe it just appears that way with the benefit of hindsight, or the intervention of revelation.

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God says in the Last Revelation, 'And We did not create the spirits or man except for our worship.' (The 'We' is a royal we, not plural)

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So there's our answer. There's no other reason for our existence except for the worship of God.

Now, my dear fellow travellers, that throws a lot of sand up in the air. Why? Because most people say they dont believe in God, and thus can not, or will not admit that this is the purpose for their lives. Then, the question still stands, for what do you exist?

There appears to be the choice between 1) choosing to wander around ignoring that the answer is being screamed at you, saying 'Im going to figure this out myself', which runs the risk of remaining lost until death, and 2) Allowing the answer to be given to you by an 'other' who is trying to underline the simplicity of the answer.

(Actually there may be another choice of not even approaching the question, but that's another ignorance, so the overall result is the same as choice one (if you dont come to the answer)).

Well, for now thats my wee amateur philosophising, a taster for us to get our teeth into, chew over and all the rest. Please let me know what you make of it.

Are there any flaws in the logic? Should we patent the idea and take our stand as the next Descartes? Not yet methinks - I dont have the right accent.

Take care fellow dreamers.