You are not what you think you are but what you think, you are.           - Os Guinness

Frances Schaeffer deals with this subject in his book, Escape From Reason from the historical standpoint pointing back to Aquinas. This is an excellent work for pastors and others who need to know the background of modern thought. However, God does not speak through history. He speaks through His Word to convict, not just to convince. Alone "the Word of God is quick and powerful and sharper than any twoedged sword, piercing even to the dividing asunder of the soul and Spirit and of the joints and marrow, ands is a discerner of the thoughts and intents of the heart" (Hebrews 4:12).