The language of mortality is inadequate to express certain sublime and supremely spiritual topics. The concepts can be uttered but not by man with his imperfect language and lack of understanding. Hence, Joseph Smith and Sidney Rigdon could not convey many things which they saw during the vision of the three degrees of glory. Of these things, Joseph wrote, ’great and marvelous are the works of the Lord…which he commanded us we should not write while we were yet in the Spirit, and are not lawful for man to utter; Neither is man capable to make them known, for they are only to be seen and understood by the power of the Holy Spirit, which God bestows on those who love him, and purify themselves before him; To whom he grants this privilege of seeing and knowing for themselves’ (DC 76:114-7). Hugh Nibley gives a practical example of this principle.
Hugh Nibley
"’…so great and marvelous were the words which he prayed that they cannot be written, neither can they be uttered by man.’ Well, the question arises, how can you tell me something about them and the words he said? Can you give me an idea? The multitude did hear and bear record, and somebody comes and says, ’Well he said marvelous things. Did you understand it?’
"’Yes, we understood it with our hearts.’
"’Well, tell me what he said. Can you give me an idea?’
"And then he says, ’No, I can’t.’
"‘Can’t you give me some idea?’
"’No.’
"I walk into a room where there are a lot of quantum physicists, highest bracket, having a conference. I listen to them for a while and then go out. Somebody says, ’Well, Mr. Nibley, can you tell me what they said in there?’
“I say, ’Heavens, I can’t tell you. I can’t even dream what they talking about; it was way out [there].’ There are plenty of things you can hear and not report or understand or anything else. Yet at the time you could have been enormously impressed.” (Teachings From the Book of Mormon, Lecture 75, p. 358-9)