Being darkened (4656) (skotoo from skotos = darkness, gloom) (Note that Textus Receptus - KJV - has skotizo 4654) literally means to be or become dark, to cover with darkness. Figuratively, skotoo means to darken or blind the mind. It means to become unable to perceive and thus unable to understand. We see a secular use of skotoo in the following sentence “I think that the new wine has already blinded them”. It is the passive voice which means the effect of darkening comes from outside. The perfect tense speaks of a process completed in past time having present results. Paul uses the perfect tense here to show the finished and permanent result of the blinding of the mind by the "sin virus" every person ever born has inherited from Adam (Ro 5:12). The perfect tense describes the enduring state of darkness the believers at Ephesus (most of whom were Gentiles) before they were regenerated by the Gospel of grace. They were in a sense impeded by a mental fog that blotted out the divine light. Not to mention that the god of this world had blinded their eyes as Paul explained to the saints at Corinth writing... And even if our gospel is veiled (perfect tense and passive voice just as with the verb "darkened"), it is veiled to those who are perishing, in whose case the god of this world has blinded (Again perfect tense and passive voice = speaking of the permanent condition unless such a one is born again) the minds of the unbelieving, that they might not see the light of the gospel of the glory of Christ (Note that the Gospel is light for spiritual darkness), Who is the image of God. (2Co 4:3, 4-note) KJV Bible Commentary phrases it this way... Their beclouded intellect and their emotions have been darkened permanently so that they are without the faculty of discernment and are unable to distinguish clearly between right and wrong. (Dobson, E G, Charles Feinberg, E Hindson, Woodrow Kroll, H L. Wilmington: KJV Bible Commentary: Nelson) McGee explains that being darkened... means that the lost man has lost his perception of moral values. That is exactly what is being promoted in our day—a loss of perception of moral values (Ed: "Values clarification", "If it feels good...just do it", "You only go around once, grab for all the gusto you can", etc). (McGee, J V: Thru the Bible Commentary: Thomas Nelson) The only other Biblical uses of skotoo refer to the darkening of the heavenly bodies in the Revelation... Revelation 9:2 And he opened the bottomless pit; and smoke went up out of the pit, like the smoke of a great furnace; and the sun and the air were darkened by the smoke of the pit. Revelation 16:10 And the fifth angel poured out his bowl upon the throne of the beast; and his kingdom became darkened; and they gnawed their tongues because of pain NIDNTT adds this comment on the word group dealing with darkness, noting that... In classic Greek darkness applies primarily to the state characterized by the absence of light (phos) without any special metaphysical overtones. The thought is chiefly of the effect of darkness upon man. In the dark man gropes around uncertainly (Plato, Phaedo, 99b), since his ability to see is severely limited. Thus the man who can see may become blind in the darkness, and no longer know which way to turn. Hence darkness appears as the “sphere of objective peril and of subjective anxiety” (H. Conzelmann, TDNT VII 424). Since all anxiety ultimately derives from the fear of death, the ominous character of darkness culminates in the darkness of death which no man can escape (cf. Homer, Il., 4, 461). Darkness is therefore Hades, the world of the dead, which already reaches out into our world in the mythical figures of the Eumenides, the children of Skotos and Gaia (Soph., Oedipus Coloneus, 40). Freed from their proper, temporal sense, the words of this group can be used in a metaphorical sense to describe human ways of life and behaviour. Thus they can describe a man’s seclusion or obscurity. They can also indicate the secrecy, furtiveness or deceitfulness of his activity, the abstruseness of his speech, lack of enlightenment, insight and knowledge. “The word does not attain to high conceptual rank in philosophy. Mention of darkness serves to set off light; it has no philosophical content of its own” (TDNT VII 425f). (Brown, Colin, Editor. New International Dictionary of NT Theology. 1986. Zondervan or Computer version)