True in a sense, but doesn't God also reveal His Truth through natural revelation (as mentioned in Romans) to those not exposed to his special revelation (Scripture)?
He reveals some truth, but not the truth of His Son.
Interesting question. In Romans although people knew God from witnessing His handy work in nature, they did not give glory to Him. So natural revelation does not quicken the spirit. Faith comes from hearing and hearing by the word of God.
A better question is could people hear God's truth apart from written text? At one time this was possible (Abraham, Moses, Jacob, etc.). But all is carried through preachers now such as with Philip and the Ethopian or Peter and Cornellius. I have read of cases where people were worshiping God but didn't know what to call Him until someone arrived on the scene to preach the good news. But then, in those cases, someone preaches the good news.
As it relates to the 'knowledge' heading: Consider this illustration, "No matter how much you tell a man about a horse, until you tell the man that God created the horse, you have not told him the truth about the horse."
Another excellent book on Calvin's influence on the modern world was written by David W. Hall, entitled, The Legacy of John Calvin. This book describes how Calvin's theology shaped the thinking that went into the writing of our Constitution, namely, that presidents, legislators, and judges to rule and govern in the knowledge that they are accountable to God.