Who would want to be "excluded from the life of God" (Eph 4:18) and "having no hope and without God in the world" (2:12)? However, there are those who "knew God" (Ro 1:21) "because that which is known about God is evident within them; for God made it evident to them" (:19) but "they did not honor Him as God or give thanks" (:21). There is the person who thinks he knows better "taking his stand on visions he has seen, inflated without cause by his fleshly mind" (Col 2:18). However, "they became futile in their speculations" (Ro 1:21). Peter told the Jews of "your futile way of life inherited from your forefathers" (1Pe 1:18) and Paul said the Gentiles walked "in the futility of their mind" (Eph 4:17). As a result of this futility "their foolish heart was darkened" (Ro 1:21) and they became "darkened in their understanding" (Eph 4:18). "Having become callous" (:19) they became "excluded from the life of God because of the ignorance that is in them because of the hardness of their heart" (:18). It is a conscious decision. Their speculations can be composed of deceptive "doctrine, by the trickery of men" (:14) which is why Peter warned "prepare your minds for action, keep sober in spirit" (1Pe 1:13). "Let no one deceive you with empty words" (Eph 4:19). They "have given themselves to sensuality for the practice of every kind of impurity with greediness" (:19). By "speaking out words of vanity they entice by fleshly desires, by sensuality" (2Pe 2:18). "In all this they are surprised that you do not run with them into the same excesses of dissipation, and they malign you" (1Pe 4:4). "Do not participate in the unfruitful deeds of darkness, but instead even expose them" (Eph 5:11).
When they chose the wrong path they lost touch with God "because of the ignorance that is in them" (Eph 4:18) due to the "hardness of their heart" (:18). The NKJV calls it the "blindness" of their heart. However, hardness seems to imply that they have set up a barrier to truthfulness having "given themselves over" (:19). Blindness seems to be a side effect of "craftiness in deceitful scheming" (:14) "by means of the hypocrisy of liars seared in their own conscience as with a branding iron" (1Ti 4:2). The "hardness of their heart" (Eph 4:18) results in "being darkened in their understanding" (:18) producing "ignorance" (:18) which indicates they are "misguided" (Heb 5:2) because they don't "believe and know the truth" (1Ti 4:3) since they "did not receive the love of the truth" (2Th 2:10). They are "separate from Christ" (Eph 2:12) and walk "according to the course of this world . . . [via] the spirit that is now working in the sons of disobedience" (Eph 2:2). "Having overlooked the times of ignorance, God is now declaring to men that all people everywhere should repent" (Ac 17:30). "Do not be conformed to the former lusts which were yours in your ignorance" (1Pe 1:14). "Lay aside the old self, which is being corrupted in accordance with the lusts of deceit" (Eph 4:22). "Be renewed in the spirit of your mind" (:23). "Laying aside falsehood, speak truth each one with his neighbor" (:25). "You were formerly in darkness, but now you are Light in the Lord" (5:8) consisting "of all goodness and righteousness and truth" (:9). "The Spirit is truth" (1Jn 5:6) and "truth is in Jesus" (Eph 4:21). "The new self . . . has been created in righteousness and holiness of the truth" (:24).