Thank you for the replies. They have been interesting and at times surprising to read. I wasn't expecting that many people who place such an import on scientific proofs and empirical evidence would agree that the evidence they would require to change their ideas about God would be some kind of supernatural occurrence. Its interesting to me as well this idea of incontrovertible evidence and that 'all it would take was one decent miracle and everyone would believe'. It reminds me of two verses from the Quran:
"They said, “We shall never believe in you unless you cause a spring to gush forth for us from the earth. Or you have a garden of date palms and grapes, then you bring forth rivers from their midst in abundance. Or you cause the sky to fall upon us in pieces, as you claimed, or you bring Allah and angels before us face to face. Or you have a house made of gold. Or you ascend to the sky, and we will not believe in your ascension unless you send down to us a book we may read.” Say, “I proclaim the Purity of my Lord. I am nothing but human, a messenger.” Nothing prevented people from believing, when guidance came to them, except that they said, “Has Allah sent a man as a messenger?” (Chapter 17, verse 90-94)
The kinds of miracles they (the non-believers at the time of the Prophet Muhammed PBUH) wanted were more in keeping with what a 7th century bedouin would consider impressive but its still essentially the same kind of request. However, just as many posters here did which was to say that even if theoretically something did happen on that scale you would still need to make sure that its not a brain malfunction, drugs, an alien etc so too do we see this response from that same group.
But you wonder, while they mock, and when they are reminded, they remember not. And when they see an Ayah (a sign, a proof, a miracle, or an evidence) from Allah, they mock at it. And they say: This is nothing but clear magic. (Chapter 37, verses 12-15)
My point is that I dont think its a case of just give a decent miracle and everyone believes. You just need to type miracle in to youtube or google and you have hundreds of examples of so-called miracles but they are not enough to convince everyone (or for some of them anyone). What is incontrovertible to one person is not to another. Also what many of you made clear and what is the natural inclination of most people is to doubt or look for alternative explanations first. If God were to now regenerate an amputated person's leg people would not immediately attribute it to God. They would probably study that person to death to understand how it happened and if they couldnt work out how it happened they would just blame it on the limitations of human understanding at the moment and say sometime in the future will work it out. Even if it was effective to that particular group of people at that particular time and made them believers what about the people who did not witness it, or who were born after the miracle occurred etc. Would they believe in it based on the word of that original group of people or would they think we were just gullible, naive, deluded etc. Would they believe that a continent just appeared from nowhere with wildlife etc and that God appeared in the sky for us or would they think its just a myth/legend/collective delusion that people in the past believed in just like some people now do with the miracles performed by Prophet Jesus PBUH.
Looking at that example for a second did the miracles of Jesus convince everyone. I mean you would think raising someone from the dead was incontrovertible, healing at that time incurable diseases etc would convince people but it didnt everyone. If people have a vested interest in not believing you they will never accept your evidence regardless of how incredible or amazing it is. I loved reading the stories of the Prophets as a child (I know the words indoctrinated must be flashing through some of your minds right now
but my brother read the same books and he is more likely to think like you - by the way he is not significantly more intelligent then me - I know thats what some of you are thinking that now too - in fact most people who know us would think it the other way round), and it used to always baffle me how even after being shown amazing miracles people would still reject faith or they wouldnt change their behaviour anyway (as someone earlier also mentioned about not worshiping God anyway even if they were to see a miracle). Take for example the story of Moses PBUH. After a number of miracles including splitting the sea in half did his enemies believe in him. No. They chased him across the sea until they were completely destroyed.
I know for atheists this is all mumbo jumbo fairy tales but its interesting the responses of some of you that would sort of fit in with this in that you would rather believe that you were collectively having a brain malfunction or hallucinating the same thing then believe that what you are seeing before you is from God. Also your doubt in these miracles mentioned in scripture is something else which is problematic about basing faith or beliefs on them. What good does it do us now that Jesus PBUh or Moses PBUH performed those miracles when we didnt see them and so dont believe they really happened. Just like people who come after us wouldnt believe a miracle that we saw actually happened. You could say we could film it or whatever but we know special effects can make literally anything look possible so why would people believe that what they are seeing is real instead of just some manufactured fantasy.
My end point is that the Quran does not encourage us to put such huge stock in miracles because even if miracles are effective at that particular time or for that particular place, they lose their power with time as people forget and begin to doubt. A miracle would have to be performed again and again for every generation to maintain people's faith which is not beyond God but does make a mockery.
"And they say, “Why is it that no signs (miracles) have been sent down to him from his Lord?” Say, “Signs are only with God, and I am only a plain warner.” Is it not sufficient for them that We have sent down to you the Book that is being recited to them? Surely in it there is mercy and advice for a people who believe. " (Chapter 29, verse 50-51)