"An agnostic is a doubter. The word is generally applied to those who doubt the verity of accepted religious creeds of faiths."

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If it is to be established that there is a God, then we have to have good grounds for believing that this is indeed so. Until and unless some such grounds are produced we have literally no reason at all for believing; and in that situation the only reasonable posture must be that of either the negative atheist or the agnostic. So the onus of proof has to rest on the proposition of theism.

— Antony Flew