My view of what outer darkness is different from what Steve C. post on 2/04 What is the Outer Darkness in the Bible? Is it hell? (fivedoves.com) but first let's discuss what inner darkness is.  I believe inner darkness is the darkness of sin within a person that they haven't repented of.  Satan is an angel of light according to 2 Corin. 11:14, and a sinner will see his or her in Satan's light which is a different light than the true light of God's word.   For instance, a fornicator, adulterer, or homosexual would not see his or her sin as the sin of fornication, adultery or a homosexual act, but would see as it as love for another person. A person who has an abortion would not see it as a sin of pre-mediated murder, but would see it as a woman's rights. Below are some Bible verses discussing this:

Matthew 6:22-23, "The light of the body is the eye: if therefore thine eye be single, thy whole body shall be full of light. But if thine eye be evil, thy whole body shall be full of darkness. If therefore the light that is in thee be darkness, how great is that darkness!"

Luke 11: 34-35, "The light of the body is the eye: therefore when thine eye is single, thy whole body also is full of light; but when thine eye is evil, thy body also is full of darkness. Take heed therefore that the light which is in thee be not darkness.'

As for outer darkness, I believe those left in outer darkness are left behind at the Rapture in the outer darkness of the world which is a sinful place  and even darker when Satan and his angels are cast down from heaven when the Antichrist reigns on Earth for 3 1/2 yrs.  But doesn't it say that they are cast into outer darkness.  Yes, it does, but doesn't the Bible also say that Jesus vomits out the unrepentant, sinful Laodiceans out of His mouth. He doesn't literally do so, but it does mean they are not inside the body of Christ and won't be part of the Bride that's raptured to heaven and will be left behind in the outer darkness of a sinful world where they will be weeping and gnashing their teeth.  They don't have the clean and white linen garment which represents the righteousness of the Bride because they haven't repented of their sins.