I know this sort of threads tend to stirr up trouble - John McLaughlin probably first went to search his longrifle to shoot me before he even opened this thread!

- but I believe most members of this site can live with stirred up troubles.
Anyway, here's a humble attempt of mine to offer a reasonable argumentation to explain why I don't believe in God. I invite all the faithful to critically examen my feeble notions and / or make an attempt of their own to produce a reasonable argumentation for their point of view. I also invite all atheists to be every bit as critical - we may both
not believe in God, but we might
not believe in him for very different reasons.
So, why don't I believe in God? Well, not for one specific reason - I would almost add 'obviously' to that phrase - but for a number of reason which I happen to find reasonable:
1. The phenomenon which I would call something like the 'God paradox' - though it isn't really a paradox.
Billions of people on this world believe in a God or multiple Gods or a deity or a divine principle or something and yet - to the best of my knowledge there isn't even an attempt at formulating a universally acceptable definition of what 'God' is supposed to be.
Next time somebody tells you that he or she is a believer, that he or she believes in God, act very foolishly and ask "What do you mean by 'God'? What is (a) 'God'?"
Many will find it less than easy to answer that question and frankly, I personally tend to believe that the only true answer would be "What I've been told (by parents, teachers, spouses, etc.)"
I find it hard to believe in something if I don't even know
what it is I should believe in.
2. There is a scientific principle that I find very intelligent: extraordinary theories or claims require extraordinary proof.
Is this the case for 'God'?
Of course, since we don't even know what 'God' is - at least:
I, at this point in my life, must honestly admit that I could produce a valid and universally acceptable definition - it's pretty hard to determin what sort of proof we are looking for.
But allow me to make a humble attempt:
If there is one characteristic all religions and all Gods seem to have in common, it's their special relation with man. I don't know of a single religion based on a careless, apathic God or a bunch of those.
Now this special relation usually seems to be determined by meaning, by a goal, by a special, higher plan this Deity is having with Mankind.
Do we find any clue to a special, higher plan, to a unique possition of Man amongst all other elements of Creation? I can't say I see any proof of that. Nothing the Homo sapiens has achieved adds up in such a way that it can make us forgt the Shoah, the genocide in Rwanda, Hiroshima, the humanitarian conflict in Darfur, ... all the attrocities mankind has bestowed upon his fellow men and continues to bestow upon them.
The instant you start thinking of those events, the very notion of a Higher Goal becomes laughable.
3. A lot, if not all religions, are tautologies. The Qu'ran is said to be the word of God and is therefor utterly useless to proove the existence of (a) God. Because the belief in the existence of God is a premise to believe in the value of the Qu'ran. So, in order for the Qu'ran to be able to proove to you the existence of God, you must first believe in the existence of God.
The Bible doesn't do much better. In Genesis God starts to create the world and the universe and land and man, but the very question 'What IS God?' is never raised. Genesis can only proove to you that God is real if you already believe that God is real.
Most, if not all, proof for the many variations on the divine theme theme are defined and developped in works that already assume the existence of such a deity - all religions appear to be cyclic tautologies with very little persuasive arguments for those who watch the circle from the outside.
If there really was such a massive, all-defining force as a God floating through reality, why has He touched so little outside of religion?
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Le bon sens est la chose du monde la mieux partagée; car
chacun pense en être si bien pourvu que ceux même
qui sont les plus difficiles à contenter en toute autre chose
n'ont point coutume d'en désirer plus qu'ils en ont.