True Christians have no reason to be in the dark. We are told in verse 21 that God had directed John to write unto the saints because they knew the truth. There are many things that professing Christians do to dumb down the truth, but God is truth and He has made His truth available to all. Only those who are truly saved have the ability to grasp the truth. The Holy Spirit indwells every true child of God and thus we can learn all that God has for us. Since the time of Christ, the local church has been the training ground for the saints. It is the place where the Word of God is to be exalted and proclaimed the loudest and clearest. From there, we go into the highways and byways and declare the truth as well.
We have talked of the ecumenical movement and the New Evangelical movement in the past. These are two well organized groups that are led by ungodly men and women who desire to keep people from knowing the truth. They would not openly declare that, but that is their goal. In my lifetime there has been a steady progression of deception coming from both of these groups. Like the illustration of the frog in the pot, most of those involved in these groups have not been able to recognize the increased deception. A few have responded humbly to the work of the Holy Spirit in their hearts and they have been saved and rejected that spirit of antichrist and have left those corrupt groups. Some of those have not continued to listen to the work of the Holy Spirit and they have not joined true churches where they can grow and serve the Lord. Some have obeyed God and the result is that there are some true churches that are seeking to honour God and help people to walk in truth.
John wrote that there is no lie of the truth. It is imperative that born again Christians build solely upon the truth — the Word of God. It is a shame when a church ignores any doctrine and still tries to suggest they are a true church. A true church must constantly be examining its teaching to be sure that it is not drifting away from the truth. The pastor must be a man of God. Acts 6 shows us that the pastor cannot get side-tracked into other things that are necessary, but they are not the main thing. He needs to be in the Word and in prayer in order to be able to keep the church he is called to lead, on the right path.
Every true child of God has a desire to know the truth. Curiosity is something we as people are known for. It is important to let God lead us in the right way. Curiosity in and of itself is not always good. For several years China and other countries researched different viruses to develop one that they could unleash on the world to cause sickness and death. Other countries also have bio-labs that are designed to find out ways to harm people. That is curiosity that has gone off the rails.
Moses was feeding his father-in-law’s sheep when God called out to him from a burning bush. Moses did not hear a voice at first. He saw a bush that was burning but not being consumed. He chose to take a closer look at this phenomena. When God had his attention, He spoke to him and gave him the initial directions to become the leader of the nation of Israel.
There is no substitute for the careful study of God’s Word. Much of the higher learning of our time, destroys the careful study of God’s Word. Too much of man’s philosophies get in the way of the truth. We need to be studying, but we do not need to seek to have a degree tacked on to our names. Paul was a faithful student of God’s Word and he was greatly used of God. I have heard some preachers refer to him as Dr. Paul. However, you will never find that title in the Bible. The title “Dr.” does not make the man wiser than the one who has been faithful without the “Dr.”
God’s man needs to focus on reading God’s Word first of all and then God can help him to know how to “read” the people he is to minister to. Timothy was commanded by Paul:

I Timothy 4:13 Till I come, give attendance to reading, to exhortation, to doctrine.