In verse 16, Mormon taught a very significant new concept. He explained that the spirit of Christ—or what today is more often called the “Light of Christ”—is given to everyone. And this source of divine light can help us make righteous judgements: “The Spirit of Christ is given to every man, that he may know good from evil; wherefore, I show unto you the way to judge.” The idea that things “invite” people to do good (7:13, 16) is a very open part of the generously repeated message of the Book of Mormon to all the world.
There was a lot of emphasis on “light” in Christ’s Sermon on at the Temple. For instance, Christ wanted his followers themselves to become “the light of this people,” much like a candlestick (oil lamp) gives light unto a room, or like a city on a hill can give light to surrounding areas (3 Nephi 12:14–16). Jesus also taught, “The light of the body is the eye; if, therefore, thine eye be single, thy whole body shall be full of light” (3 Nephi 13:22). The eye is the organ by which we discern between physical light and darkness. Now, here in Mormon’s discourse, he also is discussing light and discernment. His ultimate purpose is to help his listeners discern how to “lay hold upon every good thing” (Moroni 7:18). It can be achieved through faith, hope, and charity. Thus, he introduces the theme of the rest of his talk, having built a solid foundation upon the words of Christ, explained, as needed to his audience’s circumstances.
David A. Bednar, “Quick to Observe,” BYU Devotional Address, 2005, online at speeches.byu.edu: “I repeat again for emphasis the truth that discernment is a light of protection and direction in a world that grows increasingly dark. In these latter days you and I can press forward safely and successfully through the mist of darkness and have a clear sense of spiritual direction. Discernment is so much more than recognizing right from wrong. It helps us to distinguish the relevant from the irrelevant, the important from the unimportant, and the necessary from that which is merely nice. The gift of discernment opens to us vistas that stretch far beyond what can be seen with natural eyes or heard with natural ears. Discerning is seeing with spiritual eyes and feeling with the heart—seeing and feeling the falsehood of an idea or the goodness in another person. Discerning is hearing with spiritual ears and feeling with the heart—hearing and feeling the unspoken concern in a statement or the truthfulness of a testimony or doctrine.”