Ephesians 4:18

2. Having the understanding darkened - This is the second instance alleged by the apostle of the degradation of the Gentiles. Having no means of knowledge, the heart, naturally dark, became more and more so by means of habitual transgression; every thing in the Gentile system having an immediate tendency to blind the eyes and darken the whole soul.

3. Being alienated from the life of God - The original design of God was to live in man; and the life of God in the soul of man was that by which God intended to make man happy, and without which true happiness was never found by any human spirit: from this through the ignorance that was in them, δια την αγνοιαν την ουσαν , through the substantial or continually existing ignorance, which there was nothing to instruct, nothing to enlighten; for the most accurate writings of their best philosophers left them entirely ignorant of the real nature of God. And if they had no correct knowledge of the true God they could have no religion; and if no religion, no morality. Their moral state became so wretched that they are represented as abhorring every thing spiritual and pure, for this is the import of the word απηλλοτριωμενοι (which we translate alienated) in some of the best Greek writers. They abhorred every thing that had a tendency to lay any restraint on their vicious passions and inclinations.

4. Blindness of their heart - Δια την πωρωσιν· Because of the callousness of their hearts. Callous signifies a thickening of the outward skin of any particular part, especially on the hands and feet, by repeated exercise or use, through which such parts are rendered insensible. This may be metaphorically applied to the conscience of a sinner, which is rendered stupid and insensible by repeated acts of iniquity.