Col. 2:4 I tell you this so that no one may deceive you by fine-sounding arguments. For though I am absent from you in body, I am present with you in spirit and delight to see how orderly you are and how firm your faith in Christ is.
People can be very persuasive. There always has been those who say things that sound pretty convincing, whether it's true or not. The church has been plagued by such people ever since its conception. There are those who are masters at taking the Scriptures out of context, twisting them to say what they want them to say, and mingling them into false teachings in such a way as to make them sound true. Many people have been deceived and base their lives on things that simply are not true.
The only way to be sure that what you believe to be true is to stay personally grounded in the Word of God. Each of us must be students of the Word. We must stay closely connected to the Lord so that when the Holy Spirit speaks to us we will recognize His voice and listen to Him. We must know for certain what God's Word says and what it means. We must be so grounded in the truth from God that we can discern that which is truth from that which is false.
It was the Apostle Paul's passion in life, to see people build their lives on that which is true from God and not the beliefs and opinions of man. Paul took great delight in knowing that people were properly understanding what God was teaching them. He preached and wrote about that which God revealed to him, and only that which came from God. He knew he was proclaiming truth because he was focused on Christ alone and spent much time alone with him.
How firm is your faith? Are you absolutely sure of what you claim to believe? Can you say with confidence that what you believe is from God because you are so close to Him that when He speaks you can hear Him speak? Only those who stay near to the heart of God can be sure that they are basing their lives on that which is true and not untruth.