Nephi is inspired to prophecy to his audience that destruction will surely come to them save they should reform their lives and return to the fold of Christ. Their evil attitudes and character produce vile acts and propel them toward chaos and total spiritual eclipse. President David O. McKay testifies that a person’s actions are shaped by his inward thoughts and demeanor:
Charles Dickens makes impressive use of the above fact in his immortal story, Oliver Twist, wherein Monks is introduced first as an innocent, beautiful child; but as “ending his life as a mass of solid bestiality, a mere chunk of fleshed iniquity. It was thinking upon vice and vulgarity, that transformed the angel’s face into the countenance of a demon.” …
I am trying to emphasize that each one is the architect of his own fate, and he is unfortunate, indeed, who will try to build himself without the inspiration of God, without realizing that he grows from within, not from without… .
No man can disobey the word of God and not suffer for so doing. No sin, however secret, can escape retribution. True, you may lie and not be detected; you may violate virtue without its being known by any who would scandalize you; yet you cannot escape the judgment that follows such transgression. The lie is lodged in the recesses of your mind, an impairment of your character that will be reflected sometime, somehow in your countenance or bearing. Your moral turpitude, though only you, your accomplice, and God may ever know it, will canker your soul. (Gospel Ideals: Selections from the Discourses of David O. McKay [Salt Lake City: Improvement Era, 1953], 382–383)