After Nephi reads some of the words of Isaiah (from the Brass Plates) to his family, his brothers approach him with some questions. Among other truths, he teaches them about the source of prophetic knowledge.
“…My brethren came unto me and said unto me: What meaneth these things which ye have read? Behold are they to be understood according to things which are spiritual, which shall come to pass according to the spirit and not the flesh? And I, Nephi, said unto them: Behold they were manifest unto the prophet by the voice of the Spirit; for by the Spirit are all things made known unto the prophets, which shall come upon the children of men according to the flesh. Wherefore, the things which I have read are things pertaining to things both temporal and spiritual.” (1 Nephi 22:1-3)
– Who is the Spirit? And, how does He communicate with God’s children living on earth?
-Are their other spirits influencing those on earth besides the Spirit? (see The Temptations of the Devil Blindeth Eyes and Hardeneth Hearts)
-How can someone know they are receiving direction from the Spirit, who is a member of the Godhead, instead of from another spirit (which spirit will be at best a less than perfect source of knowledge and enlightenment)?