In Luke 11:35 Jesus said a very interesting thing - He said "Beware that the light that is in you is not darkness". On the surface, it makes no sense...how can light be darkness, until we understand it from God's perspective. From His point of view, "light" means "revelation knowledge", i.e. knowledge revealed to us by God himself by His Spirit. It is by the Holy Spirit's  ministry to us that we first come to Christ and see Him as our Savior and throughout our walk with Him the Holy Spirit continues to "lead us and guide us into all truth". So here, Jesus is saying be sure that the revelation you have of me is accurate and true and pure for if it is a false revelation it could cost you your very soul.
He said if the light that is in you is darkness - how great is that darkness! Because anyone in this circumstance believes their darkness is light! They can never find their way out of this type of darkness because they're not looking to - they think they're in the light! Every cult on earth thinks they're in the light, from the big ones like Jehovah's witnesses and Mormons to the smallest ones, they all believe their false revelation of God is the real one. So do denominations who are teaching and believing false doctrines. They, each and every one, all 33,000 of them, believe their false teachings are true.
Those who say they can see when they are actually blind are in the worst place of all, for they can't be taught. If you show them truth, they'll reject it because they think the truth is a lie and a lie is the truth. Pride keeps us all blinded to truth - the truth of our own condition as well as the condition of others. Himility (actually humility but i made a typo and i think I'll keep it...I just made up a new word....himility....the act of focusing ourselves on Him and not on us). Humility, teachableness, these are anti-dotes to blindness caused by pride. We must never think we know it all but we must confess we know the One who does know it all, who generously shares His knowledge and wisdom and understanding with us, who, when we ask for wisdom, does not upbraid us or rebuke us but gives it to us freely, but we must also continually remind our hearts - it isn't knowledge we are seeking and pursuing with all our hearts and minds, it's Him.
Knowledge and understanding are byproducts of knowing Him. Without Him, without the Holy Spirit, true wisdom and understanding can never come. The greatest Theologians on earth have nothing if they cannot love. Hearers and doers please God, not hearers only. He is greatly pleased when we remain teachable and He is able to prune false doctrines from our souls. Amen.