What is the greatest heresy among people today who consider themselves Christians? Is it the denial of Christ's deity, or the idea that "A good God would never send people to hell"? Is it legalism or its opposite, licentiousness? What is the greatest heresy propagated among people today who consider themselves Christians?
The answer, I believe, is Hellenistic thinking. Another word for Hellenistic thinking is deism, the idea that an impersonal God (or gods) set the world in motion, then left it up to man to decide his own fate without any help from above.
As most believers will acknowledge, the main tenet of Christianity is the belief in a PERSONAL God who deeply cares for and involves Himself in His creation. Many know the song "Jesus loves me, for the Bible tells me so," but to them those words are like a pat on the back by a mannequin. Such people have essentially been told, "Be warm and well fed," but they never received any true food or warmth from people calling themselves "Christians."
The problem with such people isn't a lack head of head knowledge; it's a lack of heart knowledge.
The spirit of anti-Christ has blinded their eyes, making Jesus Christ appear to them as an impersonal God, as opposed to Emmanuel, God with us, who came in the flesh, as a man - A man tempted in every way as we were, suffering every temptation a man can possibly suffer, yet without sin.
Many believers cry to God for help in overcoming temptation, berating themselves over their shortcomings while forgetting that Jesus Christ, because He came in the flesh, is more than able to help them. Determined not to "throw their brains away," they end up turning Christianity into a playground of "this program and that program," "this advice and that advice," "this method and that method," when all they really need is Christ.
That's what Paul called starting with the Spirit, but ending up in the flesh.
We who believe in Christ must resist the heresy of Hellenistic thinking and embrace the one who because He came in the flesh is more than able to save us - in every way a person can be saved.
Scriptures: Romans 10:9-10, Galatians 3:3-7, Hebrews 2:14, Hebrews 5:5-9, James 2:15-16, and I John 4:3