Mormon has told us how to judge, that we may know good from evil. He said: “The way to judge is as plain, that ye may know with a perfect knowledge, as the daylight is from the dark night. For behold, the Spirit of Christ is given to every man [we often call it the light of Christ, or conscience], that he may know good from evil; wherefore, I show unto you the way to judge; for every thing which inviteth to do good, and to persuade to believe in Christ, is sent forth by the power and gift of Christ; wherefore ye may know with a perfect knowledge it is of God” (emphasis added).
In judging what we wear, what we listen to, what we read, and what we watch, we can know perfectly well whether or not it is good for us—if it is uplifting, if it is inspiring, if it will bring us to Christ, or if we would feel comfortable wearing it, listening to it, reading it, or watching it with him present. When exposed to immorality, violence, profanity, vulgarity, or the promotion of deviant behavior, our spirits start squirming. A lot of what the world is trying to feed us will make us sick. It is junk food. See also Doctrine and Covenants 50:23–24.
The criteria, then, for discerning good from evil—how we can judge what is good for us and what is bad for us—may be summarized as follows:
1. We may know with a perfect knowledge that everything that invites us to do good, that persuades us to believe in Christ, is from God.
2. We may know with a perfect knowledge that everything that persuades us to do evil and believe not in Christ but deny him and serve him not, is from the devil. Neither the devil nor his angels nor anyone who subjects himself to the devil will persuade us to do good.
3. We should listen carefully to our conscience. Elder Richard G. Scott reminded us that what we call conscience, God calls the Spirit of Christ.5 President Joseph F. Smith said: “It is by the spirit which lighteth every man that cometh into the world that our minds are quickened and our spirits enlightened with understanding and intelligence. And all men are entitled to this. It is not reserved for the obedient alone; but it is given unto all the children of men that are born into the world.”6 For baptized members of Christ’s Church, conscience is a powerful guide. President Spencer W. Kimball once said that he would challenge any normal baptized persons who said they did not know they were doing wrong (see commentary at 2 Nephi 15:20).7