H.L.A. Hart is widely acknowledged as the most important writer and thinker of the 20th century in the discipline of Anglo-American legal philosophy. His debates with Harvard’s Lon Fuller, author of "The Case of the Speluncean Explorers," and his later debates with his former student, Ronald Dworkin, on the nature and function of law in our legal system, changed the way most scholars approach modern legal problems.

In Hart’s seminal masterpiece, "The Concept of Law," first published in 1961, he presciently discussed a hypothetical situation that we can now say actually came to fruition on Jan. 6, 2021. In Chapter IV, on the relation between sovereign and subject, he asks why subjects have the “habit of obedience” to the lawgiver and the law. He posits a mythical figure, called Rex I, who is the lawgiver and whom everyone obeys, and he asks what is to happen if Rex I were to die or otherwise leave office. He describes such circumstances as a “transition period” and he emphasizes that any good legal system should insist on a peaceful transfer of power between Rex I and his successor, Rex II. He says: