9 For this reason also, since the day we heard of it, we have not ceased to pray for you and to ask that you may be filled with the knowledge of His will in all spiritual wisdom and understanding, 10 so that you will walk in a manner worthy of the Lord, to please Him in all respects, bearing fruit in every good work and increasing in the knowledge of God; Colossians 1:9-14 (NASB) (Read verses 11-14 on the site)
We live in a time of deep deception. Even genuine Christians can be deceived if they are not exceedingly careful. It is imperative that, even though we must remain in the world for a time, we must not be of it. The Church has been under heavy attack since Acts 2. It is a wise and discerning thing for us to understand that God uses this to purify, cleanse, and teach the Church. It is as we address heresy that doctrine is developed or our understanding of God and His ways becomes more defined for us.