Joseph Smith "We never can comprehend the things of God and of heaven, but by revelation. We may spiritualize and express opinions to all eternity; but that is no authority."
Now let's not misunderstand how this works. It takes revelation to know the things of God and of heaven. And it takes revelation to understand revelation. The Lord explains this matter thus:
D&C 18:34 These words are not of men nor of man, but of me; wherefore you shall testify they are of me and not of man;
35 For it is by my voice which speaketh them unto you; for they are given by my Spirit unto you, and by my power you can read them one to another; and save it were by my power you could not have them;
36 Wherefore, you can testify that you have heard my voice, and know my words
Now what does this mean? We can physically read the words aloud without the Holy Ghost. But as far as God is concerned that isn't the same thing. We can't read them as revelation unless we read them by the power of the Holy Ghost. When they are read by the power of the Holy Ghost, then they are received by the power of the Holy Ghost, and it is as if they were revealed to us in the first instance.
And when they are not read by the power of the Holy Ghost we cannot have the revelations of God, even when they are standing right before us printed on the page.
Thus revelation both begats revelation and is necessary to understand revelation.
Elder McConkie's description was thus:
"True it is they were first proclaimed by others, but they are now mine, for the Holy Spirit of God has borne witness to me that they are true, and it is now as though the Lord had revealed them to me in the first instance. I have thereby heard his voice and know his word."