Ephesians 4:18

“Having the understanding darkened, &c.] Not that the natural faculty of the understanding is lost in men, nor the understanding in things natural and civil, and which is quick enough, especially in things that are evil; but in things spiritual it is very dark and ignorant, as about the nature and perfections of God, his holiness and righteousness; about sin and the consequences of it; about Christ, his person, office, and work, and salvation by him; about the Spirit, and his work of grace upon the soul; and about the Scripture, and the doctrines contained in it; and so it came to be by sin: the understanding of man was at first filled both with natural and divine knowledge; but man was not…”

“More literally, "Being darkened in their understanding," that is, their intelligence, or perceptions (compare Eph 5:8; Act 26:18; Th1 5:4-5). alienated--This and "darkened," imply that before the fall they (in the person of their first father) had been partakers of life and light: and that they had revolted from the primitive revelation (compare Eph 2:12). life of God--that life whereby God lives in His own people: as He was the life and light in Adam before the irruption of death and darkness into human nature; and as He is the life in the regenerate (Gal 2:20). "Spiritual life in believers is kindled from the life itself of God" [BENGEL]. through--rather as Greek, "on account of the…”

“Having the understanding darkened - That is, because they were alienated from the true God, and particularly because of “the blindness of their hearts.” The apostle does not say that this was a “judicial” darkening of the understanding; or that they might not have perceived the truth; or that they had no ability to understand it. He speaks of a simple and well-known fact - a fact that is seen now as well as then that the understanding becomes darkened by indulgence in sin. A man who is intemperate, has no just views of the government of the appetites. A man who is unchaste, has no perception of the loveliness of purity. A man who is avaricious or covetous, has no just views of the beauty of…”

“Having their understanding darkened, through the ignorance that is in them - So that they are totally void of the light of God, neither have they any knowledge of his will. Being alienated from the life of God - Utter strangers to the divine, the spiritual life. Through the hardness of their hearts - Callous and senseless. And where there is no sense, there can be no life. Ephesians 4:19”

“4:18 Their minds are full of darkness because their minds are closed and hearts are hard (see 2 Cor 4:4).”

“the understanding: Psa 74:20, Psa 115:4-8; Isa 44:18-20, Isa 46:5-8; Act 17:30, Act 26:17, Act 26:18; Rom 1:21-23, Rom 1:28; Co1 1:21; Co2 4:4; Gal 4:8; Th1 4:5 alienated: Eph 2:12; Rom 8:7, Rom 8:8; Gal 4:8; Col 1:21; Th1 4:5; Jam 4:4 because: Rom 1:21, Rom 2:19; Jo1 2:11 blindness: or, hardness, Dan 5:20; Mat 13:15; Joh 12:40; Rom 11:25 \*marg. Ephesians 4:19”