Truth, reason, and clear thinking are important because Christians can be doctrinally deceived—that is, they can succumb to false doctrine. Ezekiel 34:1-7 clearly affirms that God’s sheep can be abused and led astray by wicked shepherds. Moreover, Jesus warned His followers to beware of false prophets who may appear to be good on the outside but are dangerous on the inside (Matthew 7:15-16). Why would Jesus warn His followers to beware if they could not possibly be deceived?
Jesus also warned His followers, “Watch out that no one deceives you. For many will come in my name, claiming, ‘I am the Christ,’ and will deceive many…Many false prophets will appear and deceive many people” (Matthew 24:4,11). Why would Jesus warn His followers of such deception if they could not possibly be deceived and end up believing a lie?
Likewise, in 2 Corinthians 11:2-3, the apostle Paul warned the Christians in Corinth about the possibility of being led astray from a sincere and pure devotion to Christ. Paul clearly saw the possibility of Christians being deceived and led astray by false doctrine.
In Acts 20:28-30, Paul warned the Ephesian elders to keep a close watch on the congregation and especially to watch out for false teachers, who speak “twisted things, to draw away the disciples after them” (see Ephesians 4:14; 2 Timothy 4:3-4). — Rhodes, Ron. 2010. 5-Minute Apologetics for Today: 365 Quick Answers to Key Questions. Eugene, OR: Harvest House Publishers.