Answer from Master Keisen
I believe that they call God that inexpressable presence they feel in themselves, somehow their universality.
At the end God is just a word, by naming it they made it somewhow real and so can believe in it. This is the realm of belief, which in my mind has no real basis. One should not mix up belief and faith. Faith is an internal confidence, no need to believe, and faith is most important in life. It is not so important to try to understand in what you have faith, just have it inside, you can never name it.
Once Buddha showed his closed fist saying: "If I tell you that I hold a diamond in my fist you have to believe me. If I open my hand, everyone can see the diamond, so you do not have to believe me."
Now if another planet ... probably yes, as most populations, even isolated from the rest of the world, have created somekind of belief, God, statues, magic powers and the like. An old chinese monk said: "What are the magic powers ? Draw water, carry pieces of wood." Buddhism is a spiritual way of the life, of our life in particular.
Mondo On the same theme : Buddhism
Is it necessary to cling firmly to only one name which would synthesize all the names of the Buddhas?
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You may want to see other themes of this mondo online, or ask your own question : see Mondo online : questions to zen Master Kosen Thibaut