Kevin DeYoung, The Hole in Our Holiness, 2012, p. 41-42.
The conscience is not infallible. We can have an evil conscience that doesn’t turn away from sin (Heb. 10:22). We can have a seared conscience that no longer feels bad for evil (1 Tim. 4:2). We can have a weak conscience that feels bad for things that aren’t really bad (1 Cor. 8:7-12). And we can have a defiled conscience that loses its ability to discern right from wrong (Titus 1:15).
Kevin DeYoung, The Hole in Our Holiness, 2012, p. 41-42.