Korihor asks for a sign. He does not seem to believe that he must also ask for a sign. Alma has noted that they are both simply making a statement, and that there are two different statements. What Korihor suggests is that since Alma is claiming something that differs from what may be seen, that it is Alma who must prove his point. Of course Korihor cannot prove that God does not exist, but there is some logic in suggesting that if there is a God, there might be some evidence of that.
The problem is that Alma has already established that Korihor has shut off access to the source of proof about God. By denying the Spirit, Korihor has denied the kind of evidence that would provide the very proof that Korihor rather smugly demands. Alma has had a dramatic proof, yet Korihor will not accept that.
This is the problem with those who seek signs. The signs are already available, and they have already rejected them, yet they ask for a different type of sign. The Pharisees and Sadducees in Jesus day were had much the same problem:
Matthew 16:1-4
1 The Pharisees also with the Sadducees came, and tempting desired him that he would shew them a sign from heaven.
2 He answered and said unto them, When it is evening, ye say, It will be fair weather: for the sky is red.
3 And in the morning, It will be foul weather to day: for the sky is red and lowring, O ye hypocrites, ye can discern the face of the sky; but can ye not discern the signs of the times?
4 A wicked and adulterous generation seeketh after a sign; and there shall no sign be given unto it, but the sign of the prophet Jonas. And he left them, and departed.
The Pharisees and Sadducees did precisely what Korihor has done. They ask for some sign, but they have have had signs that they have refused. In Matthew 16, verses 2 and 3 Jesus suggests that they are able to read certain signs, but indicates that they miss the important ones. God does give us signs. Remember that Alma has “all things as a testimony that these things are true” (verse 41).
This is an important distinction. God has never said that we should not have signs. What he has said is that those signs may be interpreted by the Spirit, and in no other way. With the Spirit, Alma had “all things” has his sign. By denying the Spirit, Korihor was unable to see all of those some things (verse 41).
The problem isn’t in the signs, it is in the seeker. What a seeker of signs is saying is that they are unable to discern the signs that are given, and they want something else. They are saying that they are devoid of the Spirit, and want some other type of sign. Unfortunately, even such signs cannot convince without the Spirit. When I was serving a mission in Spain this principle was taught to use forcibly and undeniably. We knocked on the door of a man who welcomed us and invited us inside. He told us that he had a story to tell us. He had received a Book of Mormon some time earlier, and had not read it. The week previously he picked up and began to read, and he began to feel that it might be an important book. He knew that he needed to pray to God to know if it were true, so he knelt down to pray. He said that as he knelt to pray he remembered that he should not ask for a miraculous sign, but certainly he thought that God could find some way of telling him that the Book of Mormon was true.
He decided to ask for a small witness, one that he might understand, but that would not be all that miraculous. It was a stormy night, so he thought to ask to hear a clap of thunder if the Book of Mormon were true. However, since it was already stormy, he decided that it would be too easy to mistake a random clap of thunder for his answer, so he decided to ask to hear the loudest clap of thunder he had ever heard. That had been just a few nights before, a night during which my companion was awakened in the middle of the night by the loudest clap of thunder he had ever heard. The thunder came, just as this man asked. As he told us this rather remarkable story, however, he also told us that it was just possible that he was imagining all of this, and so he had decided it probably didn’t mean anything. He told us he really wasn’t interested in having us teach him.
Here as a man who could not be considered wicked or perverse, but he was nevertheless insufficiently attuned to the spirit. He asked for a sign, but even upon receiving it, it did him no good whatsoever. He even recognized the miracle of the sign, but not its significance. He was precisely like the Pharisees and Sadducees of Jesus day who could read the signs in the sky, but not the signs of the time. This man could read the sign in the thunder, but not the power in the book.