Due to our sin nature, we tend to excuse the evil in ourselves (Romans 5:12; Proverbs 20:20; Jeremiah 2:35). A continual pattern of excusing evil leads to a hardening of the conscience. Romans 1:28 gives God’s response to those who persist in evil: “Furthermore, just as they did not think it worthwhile to retain the knowledge of God, so God gave them over to a depraved mind, so that they do what ought not to be done.” There is a point at which God lets go. Those who insist on keeping their sin can now sin boldly and suffer no pangs of conscience. They believe they have transcended conscience and outsmarted God. But their judgment will come when they stand before Christ (Hebrews 9:27; Malachi 3:5).
As darkness is defined by the absence of light, sin is defined by the absence of goodness (James 4:17). Since God is the very embodiment of good (Psalm 86:5; 119:68), anything contrary to His nature is evil (Romans 3:23). We learn to distinguish good from evil by getting to know God. His Word is the foundation for understanding Him (Psalm 1:1–2; 119:160; John 17:17).The closer we draw to the holiness of God, the worse sin appears (Isaiah 6:1, 5). A t-shirt may appear white against a black wall. But when you place that shirt on newly fallen snow, it appears quite dingy. Similarly, our attempts at goodness look quite dingy when placed next to the holiness of God. As we enter His presence, we start to notice how self-centered our thoughts and actions are. We see our own greed, covetousness, lust, and deceit for the evils that they are. It is only in God’s light that we begin to see ourselves clearly.
We also learn to distinguish between right and wrong by knowing the Word. It is the Bible, after all, that delineates what is sinful and what is not. The author of Hebrews speaks of those who are immature in their faith, who can only digest spiritual “milk”—the most basic principles of God’s Word (Hebrews 5:13). In contrast to the “babes” in Christ are the spiritually mature, “who by constant use have trained themselves to distinguish good from evil” (Hebrews 5:14). Note that a Christian’s spiritual senses are strengthened through “constant use” of the Word. The ability to tell right from wrong, to distinguish between Christ’s doctrine and man’s, comes by studying and applying God’s Word.
God’s Word is filled with examples of those who did right and those who did wrong. Those examples are there for us to learn what God is like and what He desires from us (1 Corinthians 10:11). Micah 6:8 gives a brief summary of God’s desire for every person: “He has shown you, O mortal, what is good. And what does the LORD require of you? To act justly and to love mercy and to walk humbly with your God.” Malachi 3:18 makes it even clearer. God says, “And you will again see the distinction between the righteous and the wicked, between those who serve God and those who do not.” Here the Lord is equating righteousness with serving Him. If good is defined as serving God, then evil is rejecting God and refusing to serve Him. Regardless of how philanthropic a person may appear to others, his good works amount to little if they are done for selfish reasons. If we make it our goal to seek God and honor Him in everything we do (1 Corinthians 10:31), we will understand right and wrong and know that our life choices are pleasing to Him (Jeremiah 29:13; 1 Peter 3:12; Psalm 106:3).