There is nothing we MUST believe in. The sense of doing good is that it is a moral choice for me, not a religious one. As to your statement "a very simple logic yet plays important factor in belief.", if THAT is why you do good, to get into paradise, you are not truly believing that you are doing god's will. You are buying your way into paradise through good deeds.

Yes, we are all accountable. But I am not accountable to god. I am accountable to my fellow human beings.

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Extraordinary claims require extraordinary evidence - Carl Sagan