I came across this passage in Ephesians, “having the eyes of your hearts enlightened, that you may know what is the hope to which he has called you, what are the riches of his glorious inheritance in the saints” (1:18). I thought, “Isn’t enlightenment a non-Christian idea? An Eastern kind of thing?”
So I looked it up. It turns out, Paul is using the verb,”??????” (photizo) for “enlighten.” The word can mean “to shine, to illumine, to bring to light, to enlighten spiritually” (see Thayer’s lexicon). The word is used 11 times in the NT and 3 other times it carries the same weight that it does here in Eph 1:18. Take a look at John 1:9, Hebrews 6:4 and 10:32.
Not only that, but the Early Church Fathers understood baptism as an “enlightenment” or “illumination.” Justin Martyer, a second century father, said that baptism “is understood as ‘illumination’ because of the mental enlightenment by those who learn these things.” (Crossroads Initiative; Another translation at ccel). That idea brought me back to Romans 1:21, where Paul talks about those trapped in sin who “became futile in their thinking, and their foolish hearts were darkened.” (ESV)
So, when we are enslaved to sin, our minds are actually affected. Sin has a mental effect. It actually corrupts our reason. Aquinas comments that “all the powers of the soul are left, as it were, destitute of their proper order, whereby they are naturally directed to virtue; which destitution is called a wounding of nature.” (II.1.85, a.3) We can’t actually think straight when we are enslaved to sin. So baptism frees us from the corruption of sin–the spiritual corruption and the mental effect. Thus a mental enlightenment occurs in baptism. Our minds are washed clean of sin’s corrupt thoughts. They are freed from corruption just as our souls are. Analogously, it’s like when you’ve just confessed your sins in the Confessional and gotten them off your chest. Not only, does your soul feel liberated from separation from God, but somehow you feel like you can think clearly again. Sin corrupts our desires. It twists our natural impulse toward good and makes it seek wrong things. Baptism frees our desires from this corruption so we can actually be like Christ and walk in the Spirit.