[Don Franzen interviews Akhil Reed Amar here.]

IN 1881, THE GREAT 19th century expositor of constitutional law Thomas M. Cooley wrote that one of the weaknesses of a written constitution — unlike Great Britain’s unwritten constitution — is that “it establishes iron rules, which, when found inconvenient, are difficult of change.” Thirty years later, in 1911, the dean of the University of Texas School of Law, John C. Townes, expressed the then-mainstream view that principles enshrined in the U.S. Constitution are both “fundamental” and “permanent.” Their meaning was thought to be fixed.

Since the mid-20th century, though, left-leaning thinkers have fought to be free from the prison of the text, especially the prison of the words of the U.S. Constitution. Though sworn to uphold the Constitution, certain Supreme Court justices have sought ways to unshackle themselves and their successors. To the extent that they have done so, it has been by finding “penumbras” and “emanations.” This all made constitutional law much more interesting to academicians: the subject became not so much about the document in the National Archives as about “wise policy” — always in the eye of the beholder and always subject to endless disputation, casuistry (in the neutral sense, if you like), and sophistry (yes, in the pejorative sense).

Now comes Akhil Reed Amar, with an exuberant, copious, and loquacious book about constitutional interpretation: America’s Unwritten Constitution: The Principles and Precedents We Live By. But he goes well beyond penumbras and emanations. Perhaps seeking a Guinness Book record, Amar identifies not just one or two Constitutions to be interpreted, but a dozen:

• The Enacted Constitution: Amar undermines the constitutional text by trying to demonstrate that we don’t actually know what the “official” version says anyway. And he goes on about “the Year of our Lord” about five times longer than one might have thought possible, debating with himself about whether that reference in the Constitution collides with the First Amendment.
   
• The Implicit Constitution: Amar relies mostly on the predicate-act canon and the whole-text canon. The duty to do X includes the authority to do Y if Y is necessary to carry out X. On the whole, he stands on pretty firm ground here.
  
  
• The Lived Constitution: You have a constitutional right “to have a pet dog, to play the fiddle, to relax at home, to enjoy family life with your loved ones, to raise your children, to wear a hat.” You get the idea. So how do you enforce your warm and cuddly constitutional right to “enjoy family life with your loved ones”? Amar doesn’t say.
  
  
• The Warrented Constitution (that’s not a misspelling but a lame pun in homage to Chief Justice Earl Warren): The Warren Court (1953-1969) honored the “spirit” of the Constitution (and the letter, too, Amar argues unconvincingly). The Warren Court, of course, represented the official unmooring of constitutional law from the words of the document that the Court was supposed to be “interpreting.”
  
  
• The Doctrinal Constitution: Amar asserts that Roe v. Wade was correct because it was “ri...