Originalism is a loosely knit family of theories of constitutional interpretation which begin with the assumption that the  Constitution has a fixed and knowable meaning, which should be adhered to by Judges, and that the meaning of the document does not evolve over time.   The key to originalism is that decisions should be made based on facts about the document when written or ratified, with minimal adjustments for the time or context in which it is interpreted. Under this method, even when a judge sees an issue that he's persuaded ought to be ameliorated somehow, if the law as written and interpreted in the light of its original intent does not support the end result sought, a ruling supporting that result is not granted.  Originalists argue that the entire point of a written constitution which explicitly grants the government certain authorities, and explicitly withholds others from it, is to restrain government, and the value of such a document is nullified if that document's meaning is not fixed. "If the constitution can mean anything, then the constitution means nothing".  Two major varieties of originalism are original intent and original meaning.

The Originalist Revival
No one scholar or judge can deserves credit for originalism as a movement in constitutional theory and practice, but in my opinion one of the crucial events in the originalist revival was the publication of Raoul Berger's book, Government by Judiciary in 1977 by Harvard University Press. As  the title suggests, Berger was very critical of the Warren court (and its aftermath in the 70s). One of the key responses to Berger was Paul Brest's article The Misconceived Quest for the Original Understanding, published in 1980. Brest's article initiated an intense theoretical debate over the merits of originalism that continues today. At various points in time, both sides have claimed the upper hand, but at the level of theory, the case for originalism has always been contested.

Originalism has had a profound influence on constitutional interpretation and the political contest over the shape of the federal judiciary. President Reagan's nomination of Robert Bork (an avowed believer in original intent) was one key moment--with his defeat by the democrats seen as a political rejection of originalism. The current Supreme Court has at least three members who seem strongly influenced by originalist constitutional theory--Chief Justice William Rehnquist and Associate Justices Antonin Scalia and Clarence Thomas.

Throughout the 1970s and early 80s, originalism was strongly associated with conservative judicial politics and conservative legal scholars. But in the late 1980s and in the 1990s, this began to change. Two developments were key. First, Bruce Ackerman's work on constitutional history suggested the availability of "left originalism" that maintained the commitment to the constitutional will of "We the People" but argued that the constitution included a New Deal constitutional moment that legitimated the legacy of the Warren Court--We the People: Foundations, published in 1991. Second, Randy Barnett (along with Richard Epstein, the leading figure in libertarian legal theory) embraced originalism in an influential article entitled An Originalism for Nonoriginalists. Ackerman and Barnett represent two trends in originalist thinking: (1) the political orientation of originalism has broadened from conservatives to liberals and libertarians, and (2) the theoretical structure of originalism has morphed and diversified from the early emphasis on "the original intentions of the framers." After the publication of Paul Brest's Misconceived Quest one heard talk that originalism was dead as a serious intellectual movement. These days one is more likely to hear pronouncements that "we are all originalists, now."

Original Intentions
Some originalists, Judge Robert Bork among them, emphasize the original intentions of the framers. Of course, there are debates about whether the framers (a collective body) had any intentions at all. And there are questions about what counted as "intentions," e.g. expectations, plans, hopes, fears, and so forth. But the most important debate concerns levels of generality. The intentions of the framers of a given constitutional provision can be formulated as abstract and general principles or as particular expectations with respect to various anticipated applications of the provision. Most theorists will assent to this point, which flows naturally from the ordinary usage and conceptual grammar of the concept of intention. The difficulty comes because the different formulations of intention can lead to different results in any given particular case. For example, the intention behind the equal protection clause might be formulated at a relatively high level of generality--leading to the conclusion that segregation is unconstitutional--or at a very particular level--in which case the fact that the Reconstruction Congress segregated the District of Columbia schools might be thought to support the "separate but equal" principle of Plessy v. Ferguson. Perhaps the most rigorous defender of the original intentions version of originalism has been Richard Kay in a series of very thoughtful articles

A major challenge to original-intent originalism was posed by Jefferson Powell's famous article, The Original Understanding of Original Intent, published in 1985. Powell argued that the framers themselves did not embrace an original intention theory of constitutional interpretation. Of course, this does not settle the theoretical question. The framers, after all, could have been wrong on this point. But Powell's critique was very powerful for those who insisted that constitutional interpretation must always return to origins. A certain kind of original-intent theory was self-defeating if Powell's historical analysis was correct. Moreover, some of the reasons that Powell identified for the framers' resistance to originalism were quite powerful. Especially important was the idea that "secret intentions" or "hidden agendas" had no legitimate role to play in constitutional meaning. In the end, however, Powell's article actually had the effect of turning originalism in a new direction--from original intention to original meaning.

Original Meaning
The original-meaning version of originalism emphasizes the meaning that the Constitution (or its amendments) would have had to the relevant audience at the time of its adoptions. How would the Constitution of 1789 have been understood by an ordinary adult citizen at the time it was adopted? Of course, the same sources that are relevant to original intent are relevant to original meaning. So, for example, the debates at the Constitutional Convention in Philadelphia may shed light on the question how the Constitution produced by the Convention would have been understood by those who did not participate in the secret deliberations of the drafters. But for original-meaning originalists, other sources become of paramount importance. The ratification debates and Federalist Papers can be supplemented by evidence of ordinary usage and by the constructions placed on the Constitution by the political branches and the states in the early years after its adoption. The turn to original meaning made originalism a stronger theory and vitiated many of the powerful objections that had been made against original-intentions originalism.

The concept of original meaning originalism in its modern incarnation has been attributed to Justice Scalia, who is reported to have introduced the idea in a series of lectures in the 1980s; his essay, Originalism, The Lesser Evil, published in 1989, focuses on "original understanding" rather than "original intent." The idea has also been traced to a brief mention in Robert Bork's The Tempting of America, but Bork did not develop the idea extensively. Original-meaning originalism was develped more extensively by Justice Scalia in his opening essay in A Matter of Interpretation. Although the distinction between original meaning and original intent can be found in a variety of early contemporary sources including an article by Robert Clinton in 1987, the systematic development of original-meaning originalism is a relatively recent phenomenon. Original meaning originalism receives its most comprehensive explication and defense in Randy E. Barnett's new book, Restoring the Lost Constitution: The Presumption of Liberty--a systematic development of the original meaning approach and critique of the original intention theory.

Originalism and Precedent
One of the biggest challenges for originalism is how to deal with precedent.  In every legal system there is a very high value placed on stability and predictability, and accepting precedent is an important part of achieving stability.  What then is an originalist to do with a precedent not based on originalist principles?  We are already beginning to see originalists coming to grips with the relationship between original meaning and precedent--both in the narrow sense of Supreme Court decisions and the broader sense of the settled practices of the political branches of government and the states. Already, originalists of various stripes are beginning to debate the role of precedent in an originalist constitutional jurisprudence. Given the conferences and papers that are already in the works, I think that I can confidently predict that the debate over originalism and stare decisis will be the next big thing in the roller-coaster ride of originalist constitutional theory.