"And while Paul was saying this in his defense, Festus said in a loud voice, "Paul you are out of your mind! Your great learning is making you mad"

Acts 26:24

Amazing insight into perspective in this remark. How can I say that; Paul is the lucid one in this duo and Felix is the one without any insight. Paul has the wisdom of heaven but Felix' view of the matter is so skewed by his focus and attention on the world that he cannot grasp the simple wisdom of Paul's argument.

How often have ones you have declared your faith in Christ before, simply shook their heads in wonder or said "How can you believe that?" It comes in many forms. Some will say "I'm glad you are happy with your religion but it's just not for me", etc. In fact what is happening is a fulfillment of I Corinthians 2, "The natural man receives not the things of God..." 

Let them think what they will, we are not the crazy ones. Sin has driven them to the brink of eternal destruction and they just don't get it, literally.