The Bible Dictionary provides the following explanation:
“The light of Christ is just what the words imply: enlightenment, knowledge, and an uplifting, ennobling, preserving influence that comes upon mankind because of Jesus Christ. For instance, Christ is ‘the true light that lighteth every man that cometh into the world’ (D&C 93:2; John 1:9). The light of Christ fills the ‘immensity of space’ and is the means by which Christ is able to be ‘in all things, and is through all things, and is round about all things.’ It ‘giveth life to all things’ and is ‘the law by which all things are governed.’ It is also ‘the light that quickeneth’ man’s understanding (see D&C 88:6–13, 41). In this manner, the light of Christ is related to man’s conscience and tells him right from wrong (see Moro. 7:12–19).
“The light of Christ should not be confused with the personage of the Holy Ghost, for the light of Christ is not a personage at all. Its influence is preliminary to and preparatory to one’s receiving the Holy Ghost. The light of Christ will lead the honest soul who ‘hearkeneth to the voice’ to find the true gospel and the true Church and thereby receive the Holy Ghost (see D&C 84:46–48)” (“Light of Christ,” 725; see also Guide to the Scriptures, “Light, Light of Christ”; True to the Faith: A Gospel Reference [2004], 96).
“Conscience is a manifestation of the Light of Christ, enabling us to judge good from evil” (True to the Faith, 96). The “Spirit of Christ” (Moroni 7:16) and the “light of Christ” (verses 18–19) are scriptural phrases that are often used synonymously.
President Boyd K. Packer, President of the Quorum of the Twelve Apostles, testified that this light is a gift that will help us discern between good and evil:
“Regardless of whether this inner light, this knowledge of right and wrong, is called the Light of Christ, moral sense, or conscience, it can direct us to moderate our actions—unless, that is, we subdue it or silence it. …
“Every man, woman, and child of every nation, creed, or color—everyone, no matter where they live or what they believe or what they do—has within them the imperishable Light of Christ” (“The Light of Christ,” Ensign, Apr. 2005, 8, 10).
President Joseph Fielding Smith (1876–1972) identified some differences between the Holy Ghost and the Light of Christ:
“The Holy Ghost should not be confused with the Spirit which fills the immensity of space and which is everywhere present. This other Spirit is impersonal and has no size, nor dimension; it proceeds forth from the presence of the Father and the Son and is in all things. We should speak of the Holy Ghost as a personage as ‘he’ and this other Spirit as ‘it,’ although when we speak of the power or gift of the Holy Ghost we may properly say ‘it.’
“The Holy Ghost, as we are taught in our modern revelation, is the third member in the Godhead and a personage of Spirit. These terms are used synonymously: Spirit of God, Spirit of the Lord, Spirit of Truth, Holy Spirit, Comforter; all having reference to the Holy Ghost. The same terms largely are used in relation to the Spirit of Jesus Christ, also called the Light of Truth, Light of Christ, Spirit of God, and Spirit of the Lord; and yet they are separate and distinct things. We have a great deal of confusion because we have not kept that clearly in our minds” (Doctrines of Salvation, comp. Bruce R. McConkie, 3 vols. [1954–56], 1:49–50).
God’s inspiration through the Light of Christ is not limited to the members of this Church only. The Light of Christ has influenced many world leaders.
“The First Presidency has stated:
“‘The great religious leaders of the world such as Mohammed, Confucius, and the Reformers, as well as philosophers including Socrates, Plato, and others, received a portion of God’s light. Moral truths were given to them by God to enlighten whole nations and to bring a higher level of understanding to individuals. …
“‘We believe that God has given and will give to all peoples sufficient knowledge to help them on their way to eternal salvation’ (Statement of the First Presidency regarding God’s Love for All Mankind, 15 Feb. 1978)” (James E. Faust, in Conference Report, Apr. 1980, 15; or Ensign, May 1980, 12).
Elder Robert D. Hales of the Quorum of the Twelve Apostles explained a relationship between the Light of Christ and the gift of the Holy Ghost:
“Each of us brings a light to the earth—the Light of Christ. …
“By using the Light of Christ to discern and choose what is right, we can be led to an even greater light: the gift of the Holy Ghost” (in Conference Report, Apr. 2002, 80; or Ensign, May 2002, 70).