The similarities and differences between faith and knowledge are repeated themes throughout Alma’s sermon. Alma never said that knowledge was bad, only that it differed from faith. In this case, he defines faith as a “hope for things which are not seen, which are true.” Those words reflect Romans 8:24: “For we are saved by hope: but hope that is seen is not hope: for what a man seeth, why doth he yet hope for?” As with many other times where the language of the Book of Mormon reflects language or phrases from the New Testament, the similarity of words is dependent upon the translator. In this case, Joseph used familiar King James Version words for a similar thought in the text he was translating.
The same underlying Greek text was translated in the Revised English Bible as: “It was with this hope that we were saved. Now to see something is no longer to hope: why hope for what is already seen?” While the meaning is transmitted in both renditions, the Book of Mormon clearly uses the KJV vocabulary to translate that meaning.
What does it mean, then? Alma is explaining that both knowledge and faith are principles upon which we may act. If we know something, we can, and will, act upon it. If we see a physical chair, we assume we can sit in it. If we know simple arithmetic, we exchange money for goods and expect correct change if we present more than is needed. Those are things that we can know.
However, there are things that we cannot know, that we cannot see. When we perform our devotions to God, we hope and have faith in their effectiveness, but cannot act upon knowledge. We don’t have it. What we have is the ability to act when we otherwise would not. In the secular realm, we prefer to act upon knowledge. In the spiritual realm we require a firm foundation to our actions, but it must be something other than knowledge. That is the realm of faith.