Christianity in its living principles and its outward forms is purely a matter of Divine revelation. The great error of the Church in all ages, the fruitful source of her apostacy and crime, has been a presumptuous reliance upon her own understanding. Her own inventions have seduced her from loyalty to God, and filled her sanctuary with idols and the hearts of her children with vain imaginations. The Bible cuts at the very root of this evil by affording us a perfect and infallible rule of faith and practice. The absolute perfection of the Scriptures as a directory to man was a cardinal principle of the Reformation, and whatever could not be traced to them either directly or by necessary inference was denounced as a human invention – as mere will-worship, which God abhors so deeply that an inspired Apostle has connected it with idolatry or the worshiping of angels.
~ James Henley Thornwell, The Regulative Principle Applied to Church Government