Thomas Brooks (1608 – 1680), an English Puritan, gave the church an excellent work on the tactics of Satan: Precious Remedies Against Satan’s Devices (which can be read online here). One chief way in which Satan spoils the soul is through false teaching, taught and spread by false teachers. Brooks provides seven signs of a false teacher:
1. False teachers are men-pleasers.
“Such smooth teachers are sweet soul-poisoners. “This is my warning to my people,” says the Lord Almighty. ‘Do not listen to these prophets when they prophesy to you, filling you with futile hopes. They are making up everything they say. They do not speak for the Lord! They keep saying to these rebels who despise my word, ‘Don’t worry! The Lord says you will have peace!’ And to those who stubbornly follow their own evil desires, they say, ‘No harm will come your way!'” (Jer. 23:16, 17).”
2. False teachers are notable in casting dirt, scorn, and reproach upon the persons, names, and credits of Christ’s most faithful ambassadors.
“Yes, Paul, that great apostle of the Gentiles, had his ministry undermined and his reputation blasted by false teachers: ‘For his letters,’ say they, ‘are weighty and powerful—but his bodily presence is weak and his speech contemptible’ (2 Cor. 10:10). They rather condemn him than admire him; they look upon him as a dunce rather than a doctor. And the same hard measure had our Lord Jesus from the scribes and Pharisees, who labored as for life to build their own credit upon the ruins of his reputation.”
3. False teachers are venters of the devices and visions of their own heads and hearts.
“Are there not multitudes in this nation whose visions are but golden delusions, lying vanities, brain-sick fantasies? These are Satan’s great benefactors, and such as divine justice will hang up in hell as the greatest malefactors, if the physician of souls does not prevent it.”
4. False teachers easily pass over the great and weighty things both of law and gospel, and stand most upon those things that are of the least importance and concern to the souls of men.
“1 Tim. 1:5-7: ‘Now the end of the commandment is charity out of a pure heart, and of a good conscience, and of faith sincere; from which some having swerved, have turned aside unto vain jangling, desiring to be teachers of the law, and understand neither what they say nor whereof they affirm.’ Matt. 23:23: ‘Woe unto you, scribes and Pharisees, hypocrites; for you pay tithe of mint, and anise and cummin, and have omitted the weightier matters of the law, judgment, mercy, and faith; these ought you to have done, and not to leave the other undone.’ False teachers are nice in the lesser things of the law, and as negligent in the greater.”
5. False teachers cover and color their dangerous principles and soul-deceptions with very fair speeches and plausible pretenses, with high notions and golden expressions.
“Many in these days are bewitched and deceived by the magnificent words, lofty strains, and stately terms of deceivers. As strumpets paint their faces, and deck and perfume their beds, the better to allure and deceive simple souls; so false teachers will put a great deal of paint and garnish upon their most dangerous principles and blasphemies, that they may the better deceive and delude poor ignorant souls. They know sugared-poison goes down sweetly; they wrap up their pernicious, soul-killing pills in gold! (Gal. 6:12; 2 Cor. 11:13-15; Rom. 16:17, 18; Matt. 16:6,11,12; 7:15.)”
6. False teachers strive more to win over men to their opinions, than to better them in their lives.
“Matt. 23:15: ‘Woe unto you, scribes and Pharisees, hypocrites! for you compass sea and land to make one proselyte, and when he is made, you make him twofold more the child of hell than yourselves!’ They busy themselves most about men’s heads. Their work is not to better men’s hearts, and mend their lives; and in this they are very much like their father the devil, who will spare no pains to gain proselytes.”
7. False teachers make merchandise of their followers.
“They eye your goods more than your good; and mind more the serving of themselves, than the saving of your souls. So they may have your substance, they care not though Satan has your souls (Rev. 18:11-13). That they may the better pick your purse, they will hold forth such principles as are very indulgent to the flesh. False teachers are the great worshipers of the golden calf. “From the least to the greatest, all are greedy for gain; prophets and priests alike, all practice deceit.” (Jer. 6:13).”
(The above was taken from Appendix 2, pages 142 – 144, in the PDF version linked above.)