When does a person [prophet] speak as a prophet? Do you recall the revelation in which the Lord said:

“And, behold, . . . this is an ensample unto all those who are ordained unto this priesthood (he is talking to General Authorities), whose mission is appointed unto them to go forth. . . .

“. . . they shall speak as they are moved upon by the Holy Ghost.

“And whatsoever they shall speak when moved upon by the Holy Ghost, shall be scripture, shall be the word of the Lord, shall be the voice of the Lord, and the power of God unto salvation.” (D&C 68:2-4.)

This is so when the authority is speaking by the power of the Holy Ghost. As someone has rightly said, it is not to be thought that every word spoken by our leaders is inspired. The Prophet Joseph Smith wrote in his personal diary, “This morning, I . . . visited with a brother and sister from Michigan, who thought that ‘a prophet is always a prophet;’ but I told him that a prophet was a prophet only when he was acting as such” (Teachings, p. 278). It is not to be thought that every word spoken by the General Authorities is inspired, or that they are moved upon by the Holy Ghost in everything they speak and write. Now you keep that in mind. I don’t care what his position is, if he writes something or speaks something that goes beyond anything that you can find in the standard church works, unless that one be the prophet, seer, and revelator—please note that one exception—you may immediately say, “Well, that is his own idea.” And if he says something that contradicts that is found in the standard works (I think that is why we call them “standard”)—it is the standard measure of all that men teach), you may know by that same token that it is false, regardless of the position of the man who says it. We can know that they are speaking under inspiration if we so live that we can have a witness that what they are speaking is the word of the Lord. There is only one safety, and that is that we shall live to have the witness to know. President Brigham Young said something to the effect that “the greatest fear I have is that the people of this Church will accept what we say as the will of the Lord without first praying about it and getting the witness within their own hearts that what we say is the word of the Lord.”