The prophets, both ancient and modern, have clearly taught that God knows everything. Psalm 147:5 reads: "Great is our Lord, and of great power: his understanding is infinite." In Doctrine and Covenants 38:1-2, Jesus Christ introduces himself in these words: "Thus saith the Lord your God, even Jesus Christ, the Great I AM . . . The same which knoweth all things." (See also Alma 26:35.) The Prophet Joseph Smith also clearly taught this doctrine, as is indicated in his "Lectures on Faith" which appeared in the early editions of the Doctrine and Covenants:
. . . God is the only supreme governor and independent being in whom all fulness and perfection dwell; who is omnipotent [all powerful], omnipresent [everywhere present] and omniscient [all knowing]; without beginning of days or end of life; and that in him every good gift and every good principle dwell. . . .. . . Without the knowledge of all things, God would not be able to save any portion of his creatures; for it is by reason of the knowledge which he has of all things, from the beginning to the end, that enables him to give the understanding to his creatures by which they are made partakers of eternal life; and if it were not for the idea existing in the minds of men that God had all knowledge it would be impossible for them to exercise faith in him. ("Lectures on Faith," Lecture 2, paragraph 2; Lecture 4, paragraph 11.)
Joseph Fielding Smith quotes his grandfather, Hyrum Smith, as having said: "I would not serve a God that had not all wisdom and all power." Then Joseph Fielding Smith continues, "Do we believe that God has all 'wisdom'? If so, in that, he is absolute. If there is something he does not know, then he is not absolute in 'wisdom,' and to think such a thing is absurd." (Doctrines of Salvation, 1:5.) President Smith indicates possible areas in which God is progressing (glory, honor, etc.), and then concludes, "Do you not see that it is in this manner that our Eternal Father is progressing? Not by seeking knowledge which he does not have, for such a thought cannot be maintained in the light of scripture. It is not through ignorance and learning hidden truth that he progresses, for if there are truths which he does not know, then these things are greater than he, and this cannot be." (Doctrines of Salvation, 1: 7).