2 Corinthians 11:3
But I fear, lest by any means, as the serpent beguiled Eve through his subtilty, so your minds should be corrupted from the simplicity that is in Christ.
Note 6 at 2Co 11:3: The Christian life is a constant struggle against Satan, who is trying to corrupt us. Most Christians are aware of the warfare, but they are mistaken about where the warfare is occurring. Paul made it clear that the battle is in our minds. Just as the serpent didn't come against Eve with brute force but rather used words to deceive her, likewise he tries to corrupt us through thoughts contrary to the Gospel. Notice the words "beguiled" and "subtlety." Satan's original tactic was deception, and that is still his method of operation today.
Note 7 at 2Co 11:3: The Gospel of Christ is so simple that you have to have someone help you to misunderstand it. The sad fact is that there are more than enough people who are willing and able to help us confuse the issues. In the instance of the serpent deceiving Eve, Satan took a simple truth and complicated it. God said, "Don't eat or you die." Satan made it much more complicated and deceived Eve through his sophistication. If she had just kept it simple, she would have stayed pure.
We should be wary of anyone who has a revelation that the average person cannot receive. If it is so complex that it takes a great amount of training to understand it, then it probably isn't from God. It is true that many revelations from the Lord take a lifetime to renew ourselves to; however, the truths are simple and easy to grasp. "But the wisdom that is from above is first pure, then peaceable, gentle, and easy to be intreated, full of mercy and good fruits, without partiality, and without hypocrisy" (Jas 3:17).