In contrast to the blessed state of the good is the awful state of the wicked. “Outer darkness” refers, in general, to the light/dark contrast so frequent in the scriptures. Light is life and good; dark is death and evil. Thus, “darkness” is the presence of evil.
But the mention of “outer” is also significant. It is logical to assume that it underscores the distance from the light source. The farther one goes from a light, the darker it becomes. While the wicked may still be in God’s realm, they are not close to his glory.
All scriptural occurrences of “outer darkness” also include the response of those consigned to this location. For example:
When Jesus heard it, he marvelled, and said to them that followed, Verily I say unto you, I have not found so great faith, no, not in Israel.
And I say unto you, That many shall come from the east and west, and shall sit down with Abraham, and Isaac, and Jacob, in the kingdom of heaven.
But the children of the kingdom shall be cast out into outer darkness: there shall be weeping and gnashing of teeth.” (Matt 8:10–12)
All of the other biblical examples also occur in Matthew. The contrast is between a believing Gentile, who “shall sit down with Abraham, and Isaac, and Jacob, in the kingdom of heaven,” and unbelieving Israel, who “shall be cast out into outer darkness.” The paired concepts of light/dark and inner/outer are complemented by the inclusion/exclusion of people in God’s kingdom.
This inclusion/exclusion theme is highlighted in Matthew 22:2–13. Excluded from the wedding feast, which would also be brilliantly lighted, the man who lacked a wedding garment was sent to “outer darkness; there shall be weeping and gnashing of teeth” (Matt. 22:13). While this is a parable, it must also have a natural parallel in order for the parallel to be intelligible. Rather than seeing Alma’s description as reflecting our modern understanding that sons of perdition will be consigned to outer darkness during the final judgment, we should read it for its dual symbols, with the most significant being the equation of outer darkness with exclusion from the kingdom. This exclusion would be for all of the wicked, not just those who fit the narrow definition of a son of perdition.