"Therefore, why is it that ye cannot understand and know, that he that receiveth the word by the Spirit of truth receiveth it as it is preached by the Spirit of truth?
Wherefore, he that preacheth and he that receiveth, understand one another, and both are edified and rejoice together.
And that which doth not edify is not of God, and is darkness.
That which is of God is light; and he that receiveth light, and continueth in God, receiveth more light; and that light groweth brighter and brighter until the perfect day.
And again, verily I say unto you, and I say it that you may know the truth, that you may chase darkness from among you."
Doctrine and Covenants 50:21-25
I like the whole connection here between truth and light... this scripture starts out with an education theme, talking about ideal learning and teaching... that when the Spirit of truth is present, everyone gets it. :) You don't have to explain it 300 times, or hear it 300 times, it is there, and everyone understands, and is uplifted by the experience. Obviously not all learning experiences are that ideal, but I think it is interesting that *truth* makes the difference... when we are willing to tell the truth, and when we are willing to hear the truth... and believe me, the truth is hard to present *and* hard to accept sometimes... that's when the Spirit can come in and translate it directly to our souls.
and then the scripture goes on and starts the truth/light analogy... that which doth not edify is darkness. darkness of understanding certainly, but perhaps also darkness of emotion... darkness of soul. continuing... what God presents to us is light, and the more light we receive, the more he gives... until the perfect day... when, presumably, we will be filled completely with light... like Moses when he came back from talking with God, his face was so bright the children of Israel didn't want to look at him... :) another cool thing is that there will *be* a perfect day when we know all the truth, have received all the light... that will be a cool cool day. :)
then, this last verse, which is actually leading into more stuff in the section, but it says that knowing the truth can chase darkness from us.... the more light we have, the less darkness... like the scripture that says "light and truth forsake the evil one" ... the more good we have, the less bad... and seriously... who wants the darkness? it feels like hell, literally. and I wonder... if truth is light... is it as easy to tell the difference between truth and falsehood as it is between light and darkness? how much do we deceive ourselves?