Elder Gerald N. Lund explained the impossibility of proving that there is no God:
“When questioned, Korihor categorically denies that he believes there is a God. Alma then asks, ‘What evidence have ye that there is no God, or that Christ cometh not? I say unto you that ye have none, save it be your word only.’ (Alma 30:40.)
“It is an inspired insight on Alma’s part. Korihor is not consistent in his own thinking. If we truly can know only those things for which we have empirical evidence, then we cannot teach there is no God unless we have evidence for that belief. And Korihor has no evidence.
“Korihor will consider only evidence that can be gathered through the senses. In such a system, it is much easier to prove there is a God than to prove there is not a God. To prove there is a God, all it takes is for one person to see, hear, or otherwise have an experience with God, and thereafter the existence of God cannot be disproved. But here is what it would take to prove there is no God: Since God is not confined to this earth, we would have to search throughout the universe for him. We assume God is able to move about, so it would not be enough to start at point A in the universe and search through to point Z. What if after we leave point A, God moves there and stays there for the rest of the search?
“In other words, for Korihor to say that there is no God, based on the very criteria he himself has established, he would have to perceive every cubic meter of the universe simultaneously. This creates a paradox: In order for Korihor to prove there is no God, he would have to be a god himself! Therefore, in declaring there is no God, he is acting on ‘faith,’ the very thing for which he so sharply derides the religious leaders!” (“Countering Korihor’s Philosophy,” Ensign, July 1992, 21).