Nephi has personal experience with this. When he saw the vision of the tree of life, he was taken away in the spirit that he might behold a glorious vision. Nephi is teaching that Isaiah received his prophecies by the power of that same Spirit. The Spirit is also able to make all things known unto those who are not prophets, And by the power of the Holy Ghost ye may know the truth of all things (Moroni 10:5). Joseph F. Smith taught what effect the Holy Ghost can have upon the saints as a group.
Joseph F. Smith
"That Spirit, it must be remembered, is, by way of preeminence, called 'The Spirit of Truth, which proceedeth from the Father.' He teaches all things; and brings to the remembrance of the Saints all the instructions of the Master. He guides into all truth, and as in all truth there is unity or harmony, so, it is believed that if the Saints are in possession of this Spirit, the harmony in the Church of Christ will be superior to the harmony that can be looked for or hoped for, in any other organization whatsoever. And because the Saints have free access to the Holy Spirit, and may walk within his light and fellowship and possess the intelligence which he is able to impart, a stricter harmony among the Saints may be insisted upon than in any other organization of men whatsoever." (Gospel Doctrine, p. 131)