In answering his brothers, Nephi explained that these prophecies of Isaiah were to be understood as being “both temporal and spiritual.” That is, they would literally come to pass, yet their interpretation would go beyond the event of their temporal fulfillment, for they carried spiritual or symbolic meanings also.
Nephi further explained that it is only by the spirit of revelation that such questions can be answered, saying, “For by the Spirit are all things made known unto the prophets.” It takes a prophet to understand a prophet, and it takes the spirit of revelation to understand the spirit of revelation.
Any doctrine that seals the heavens to continuous revelation will also close the door to a proper and inspired understanding of that which has already been revealed, including, of course, our ability to rightly divide the literal from the figurative.