From the earliest days, while the apostles were still living, the enemy has sown confusion in the churches about the gospel. In his last letter before his death, Paul warned Timothy in 2 Timothy 3:13, “But evil men and impostors will proceed from bad to worse, deceiving and being deceived.” He goes on to exhort Timothy to continue (the same Greek word that is translated abide in John) in the Word, which is able to bring us to salvation. If Satan can cause confusion about the gospel, everything else is affected. It is the domino that causes all the others to fall. By the way, as John Calvin notes, it is the duty of a godly pastor to drive away the wolves and to warn the flock about those who pervert the gospel. I would not be a faithful pastor if I only spoke to you about positive, heartwarming matters, but did not also warn you of these insidious errors.