Lehi had a revelatory dream, Nephi interpreted it by revelation, and their experience teaches us important truths about revelation.
Let me skip over the big, obvious, and hugely important truth to the interesting passage that I noticed today. In this passage, Nephi reveals that Lehi simply didn’t notice key parts of his own dream.
26 And they said unto me: What meaneth the river of water which our father saw?
27 And I said unto them that the awater which my father saw was filthiness; and so much was his mind swallowed up in other things that he beheld not the filthiness of the water.
28 And I said unto them that it was an awful gulf, which separated the wicked from the tree of life, and also from the saints of God.
29 And I said unto them that it was a representation of that awful hell, which the angel said unto me was prepared for the wicked.
Let’s not get sidetracked with the double meaning of the water, which Nephi says is at the same time the thing that separates the abode of the wicked (hell) from God while also being itself hell, which tends to suggest that separation from God is what constitutes hell. Never mind all that. Lehi didn’t notice that the water was filthy, which was the key to Nephi’s interpretation of the water.*
The minor truth is that at least some visions don’t consist of ideas or concepts that the brain interpretes visually. They can be actually presented as visual information to the mind to be processed and mis-seen just like the things we see with our eyes.
The more important truth is that we can screw up revelation, because to err is human, and it is to humans that revelations are made. Some of us take this truth for granted as a private addendum to the revelatory process made on the basis of our experience. Others reject it, probably because too many use the human fallibility of revelation as an excuse to jump into Lehi’s gulf. Like it or not, the Book of Mormon supports it. It is nothing to be ashamed of.
*The “filthiness” of the water fits with Hebraic culture.