To use Paul's analogy, our spiritual diet must not be a mixture of true and false doctrines. In this area of life, a mixture produces nothing good (James 3:11-12). We must make every effort to separate the true food from the false if we are to grow and qualify for the Kingdom of God. This is a responsibility that falls on each of us—we cannot leave it to others! We must acknowledge the source of the false teaching—Satan, his demons, and his false ministers—to truly appreciate the seriousness of heresy.
Like Peter, Paul warns about heresies within the church: "Now the Spirit expressly says that in latter times some will depart from the faith, giving heed to deceiving spirits and doctrines of demons" (I Timothy 4:1). The Greek word planos, translated as "deceiving" (NKJV) or "seducing" (KJV), is the same word from which we derive the English word "planet." It conveys the idea of wandering. To the astronomers of ancient Greece, the planets appeared to wander in a heaven populated by other, relatively fixed lights. Thus, evil spirits induce people to wander from the true path of God's Word. These are the principalities and powers against which we wrestle (Ephesians 6:10-12).
Heresy is not always easily detected because Satan usually camouflages the lie with a large measure of truth. He is a master of deceit. Because the people of the world are so ignorant of God, Satan can tell them virtually anything, and they will believe it. But with us he generally does not directly challenge or obviously and blatantly misquote Scripture. His confrontation with Jesus, beginning in Matthew 4:1, is a classic example. He subtly twists the intent of a scripture to bend it into a wrong application or understanding. At other times, he will appeal to our vanity to get us to react to his suggestions without thinking.
The Bible gives only a few specific doctrines with which seducing spirits, heresy or false ministers are directly associated. However, do not be fooled that so few doctrines are directly mentioned with the word "heresy" attached. No doctrine is sacrosanct to demons. They will attack the people of God in any spiritual area. The Bible makes it very clear that demons are our major, major enemies, and deception that leads us into sin is their game!