There are about twenty easily named religious groups in the world. Of the twenty, seven are major religious groups accounting for more than 60% of the world's population. Every one of these groups make truth claims. More often than not, these claims are contradictory. Any wife person would immediately decipher that they all cannot be correct. A true seeker of truth therefore, needs to be able to identify and pick out the counterfeits.
Within Christianity, there are also heretical groups. They use the Christian lingo, consider the Bible to be a Holy book, hold church services, and even believe some of the same things we believe. The problem with them is that they have trampled upon some of the essential doctrines of the Historic Christian Faith. The Apostle John warned us that "... it is the last hour; and just as you heard that antichrist is coming, even now many antichrists have appeared; from this we know that it is the last hour." 1 John 2:18.
Christians need to be able to know the original so well that they can detect a counterfeit a mile away. We need to be able to discern the lie, even if it is gift-wrapped with the skin of truth.
This page would provide a collection of articles about identifying and countering counterfeits and heretics.