A lthough James Madison has been invoked by justices and judicial scholars for over 100 years, Madison's principle of religious liberty has never been fully grasped or adopted by the Supreme Court. Judges and scholars have failed to understand Madison's radical but simple teaching that religion is not part of the social compact and, therefore, that the state may not take religion within its cognizance. In this article I set forth Madison's principle of "noncognizance" in light of the social compact theory he articulates in the "Memorial and Remonstrance." I then attempt to show how it consistently explains Madison's political actions and writings on religious liberty. I conclude by explaining how a "Madisonian" approach, properly understood, would adjudicate the First Amendment's religion clauses.