Why do unvirtuous thoughts specifically cause the Spirit to depart? Indulging in thoughts related to our other carnal appetites do not do the same thing. For example, if I daydream about gorging on a luscious chocolate cream pie, I don’t lose the Spirit. Neither if I lust and drool over a big pot of homemade Macaroni & Cheese (with bacon!). So why is the Spirit so sensitive to this one particular carnal appetite? Thanks in advance for your kind wisdom.
Can I just say that reading your question made me suddenly hungry? Anyway, to your question.
We know that the members of the Godhead, Heavenly Father, Jesus Christ and the Holy Ghost are one. We know of the love that Heavenly Father and Christ have for us. While we don’t often speak of it, we can also understand that because They are One, the Holy Ghost loves us as well. He wants to help us. His job is to teach, comfort, and guide us. If He left us alone every time we sinned or are weak, we would never get to feel His comforting guidance or learn from Him, because we are all sinners. So when He does leave us that should be a warning to us of how serious the mistake we are making is. Feeling the Spirit depart should be a clear sign that we are making a choice that is taking us not only away from the Holy Ghost, but Heavenly Father and Christ also.
So why is having unvirtuous thoughts so serious? Because breaking the Law of Chastity is so serious. Elder Jeffrey R. Holland gave a wonderful talk about this very thing in 1988 at a devotional at BYU. I will paraphrase some of his thoughts and share some direct quotes as well.
First, he reminds the students that aside from sinning against the Holy Ghost, immorality is second only to murder as one of the most serious sins we can commit.
“Clearly God’s greatest concerns regarding mortality are how one gets into this world and how one gets out of it. These two most important issues in our very personal and carefully supervised progress are the two issues that he as our Creator and Father and Guide wishes most to reserve to himself. These are the two matters that he has repeatedly told us he wants us never to take illegally, illicitly, unfaithfully, without sanction.”
He goes on to talk about how it is generally accepted that killing people is wrong. It’s not something most of us would ever even consider doing.
“As for the taking of life, we are generally quite responsible. Most people, it seems to me, readily sense the sanctity of life and as a rule do not run up to friends, put a loaded revolver to their heads, and cavalierly pull the trigger. Furthermore, when there is a click of the hammer rather than an explosion of lead, and a possible tragedy seems to have been averted, no one in such a circumstance would be so stupid as to sigh, ‘Oh, good. I didn’t go all the way.'”
He points out that “all the way or not the insanity of such action” is obvious. In the case of chastity, however, we are not so careful. Some of us are irresponsible.
“What would in the case of taking life bring absolute horror and demand grim justice, in the case of giving life brings dirty jokes and four-letter lyrics and crass carnality on the silver screen, home-owned or downtown.”
So you see, Robert, in a world where immorality is taken very lightly, the Holy Ghost wishes for us to remember that it is something our Heavenly Father takes very, very seriously. As Elder Holland said, God reserves for Himself how we get into this world and how we get out of it. We should heed the warning of the Holy Ghost and take them both equally seriously.