A mentor or an exemplary principle. Presumably this expression refers to the light of a lantern or beacon guiding someone through the dark. The earliest transference of this idea was religious, “light” referring to God or the church. Thus the American Transcendentalist Theodore Parker wrote, “We look to Thee; Thy truth is still the Light which guides the nations, groping on their way.” Sometime in the latter part of the nineteenth century the term began to be used for secular mentors of various kinds.