Another doctrine which is most important when cultic matters are evaluated is the biblical doctrine of sin. The absence of a belief in sin is the hall-mark of the cults. That is what I meant earlier when I said cults are often preached from so-called Christian pulpits. Certain men have become very popular through preaching that there is no such thing as sin, that it is very wrong to talk about sin, and that the Church, by preaching a doctrine of sin, has kept the people from truth. Instead of a belief in sin, they say, you must believe in yourself. ‘Positive thinking’, as it is termed, is very popular in America today, and it is being preached in this country also. It sounds so marvelous – ‘There is no such thing as sin; you must not speak against yourself, you must not look down on yourself. Believe in yourself; you are wonderful if you only realized it! What the Bible calls sin is an insult to mankind; we now understand all these things psychologically.’
None of the cults like the doctrine of sin; and, of course, for the very good reason that you are never going to be popular if you preach the biblical doctrine of sin. But the cults must be popular, otherwise they cannot succeed. God is not in them, so something has to keep them going. The men and women who keep going do so by pandering to people, pleasing them and praising them.
It is exactly the same with regard to the doctrine of salvation. Obviously if the cults do not believe in sin you would not expect them to be right about salvation. They do not believe that the Son of God came from heaven to earth in order to take sin upon Himself and bear the punishment… They do not believe in substitutionary atonement.
Ephesians 6:10-13 – The Christian Warfare, pg 129-130.