Every contact that man has ever had with the universe has come to him through his Five Senses. He has gained no knowledge independently of them. We may illustrate the limitation of sense knowledge by the following example: A blind man who has never possessed the sense of sight, could never know anything of color; a deaf man who had never heard, could never know anything of sound. So we also with our Five Senses know nothing except as it has come to our mind through these five channels. In otherwords the vast body of knowlege has come throught experimentation.
It is no wonder that these men who have only contacted the physical through their Sense perception should deny the existence of God, because they cannot find Him in the material world. They cannot find spirit nor soul through their experiments in Chemistry or Biology. You can see why they naturally would rule out the supernatural and why miracles would be impossible to them. You can understand now why a man who has never been Born Again cannot expound the Scriptures and give us their spiritual content. These senses belong to the physical body, and they can only contact matter.
Therefore, man knows only that which is physically discerned. He has learned a great deal about the universe in which he lives but nothing about the Creator. As Voltaire has said, he has been able to study the stars but himself he has not come to know.
Only a man whose mind has been illuminated by the New Birth can know God or understand His Revelation.