What is the "outer darkness"?

The phrase "outer darkness" is mentioned three times in the Bible. These three times are:

• Matthew 8:12But the children of the kingdom shall be cast out into outer darkness: there shall be weeping and gnashing of teeth.
  See All... But the children of the kingdom shall be cast out into outer darkness: there shall be weeping and gnashing of teeth.
• Matthew 22:13Then said the king to the servants, Bind him hand and foot, and take him away, and cast him into outer darkness, there shall be weeping and gnashing of teeth.
  See All... Then said the king to the servants, Bind him hand and foot, and take him away, and cast him into outer darkness; there shall be weeping and gnashing of teeth.
• Matthew 25:30And cast ye the unprofitable servant into outer darkness: there shall be weeping and gnashing of teeth.
  See All... And cast ye the unprofitable servant into outer darkness: there shall be weeping and gnashing of teeth.

First, I look for parallel passages that would help define outer darkness. An interesting connection is found in the phrase, gnashing of teeth, which occurs exactly seven times in the Bible. Here they are.

Three times the phrase is found in the verses that mention outer darkness.

One time in Luke 13:28There shall be weeping and gnashing of teeth, when ye shall see Abraham, and Isaac, and Jacob, and all the prophets, in the kingdom of God, and you yourselves thrust out.
See All.... This passage (Luke 13:28-29 [28] There shall be weeping and gnashing of teeth, when ye shall see Abraham, and Isaac, and Jacob, and all the prophets, in the kingdom of God, and you yourselves thrust out. [29] And they shall come from the east, and from the west, and from the north, and from the south, and shall sit down in the kingdom of God.
See All...) is a parallel passage to the outer darkness reference in Matthew 8:11-12 [11] 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. [12] But the children of the kingdom shall be cast out into outer darkness: there shall be weeping and gnashing of teeth.
See All.... In Matthew, the children of the kingdom are cast into outer darkness. In Luke, Jesus refers to His audience and states, "and you yourselves thrust out." Both passages are referring to the kingdom when people will come from all directions to meet with Abraham, Isaac, and Jacob. But these hypocrites who consider themselves a part of the kingdom will be cast out. So, the "outer" in "outer darkness" probably refers to being outside the kingdom of God.

• One time when the unfaithful servant is appointed his portion with the hypocrites (Matthew 24:51And shall cut him asunder, and appoint him his portion with the hypocrites: there shall be weeping and gnashing of teeth.
  See All...).
• Two times when the wicked will be gathered from God's kingdom and cast into a "furnace of fire" (Matthew 13:42And shall cast them into a furnace of fire: there shall be wailing and gnashing of teeth.
  See All..., 50). Evidently, outer darkness can also be called a furnace of fire.

All evidence points to outer darkness being identical to hell. It is called "outer" because it is outside God's kingdom. Those in outer darkness have been thrust out of the kingdom. It is called darkness because it is a place of darkness. But how can a place of fire be a place of darkness? Does not fire emit light?

First, the Bible teaches that the places of judgment (whether hell of the lake of fire) are also places of darkness. Consider these verses:

2 Peter 2:4For if God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment;
See All... For if God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment;

2 Peter 2:17These are wells without water, clouds that are carried with a tempest; to whom the mist of darkness is reserved for ever.
See All... These are wells without water, clouds that are carried with a tempest; to whom the mist of darkness is reserved for ever.

Jude 1:6And the angels which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains under darkness unto the judgment of the great day.
See All... And the angels which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains under darkness unto the judgment of the great day.

Jude 1:13Raging waves of the sea, foaming out their own shame; wandering stars, to whom is reserved the blackness of darkness for ever.
See All... Raging waves of the sea, foaming out their own shame; wandering stars, to whom is reserved the blackness of darkness for ever.

Second, experimental science demonstrates that the purer the flame and the hotter the fire, the less light will be emitted from the fire. Certainly, this is the case with hell. Even the appearance of God on Mount Sinai combined a burning fire with great darkness (Deuteronomy 4:11And ye came near and stood under the mountain; and the mountain burned with fire unto the midst of heaven, with darkness, clouds, and thick darkness.
See All...; 5:22
See All..., 23; Hebrews 12:18For ye are not come unto the mount that might be touched, and that burned with fire, nor unto blackness, and darkness, and tempest,
See All...).

I conclude therefore that "outer darkness" is yet another synonym for hell. It is a place of darkness. It is also outside the experience of God's grace. For, although God bestows His grace on both the just and the unjust while on earth (Matthew 5:45That ye may be the children of your Father which is in heaven: for he maketh his sun to rise on the evil and on the good, and sendeth rain on the just and on the unjust.
See All...; Acts 14:17Nevertheless he left not himself without witness, in that he did good, and gave us rain from heaven, and fruitful seasons, filling our hearts with food and gladness.
See All...), none of the gracious presence of God is to be found in the place of outer darkness. May we trust in the Son of God who can and will deliver us from this place. May we warn others of the evil of this place.