Constitutionalism is the idea, often associated with the political theories of John Locke and the "founders" of the American republic, that government can and should be legally limited in its powers, and that its authority depends on its observing these limitations. This idea brings with it a host of vexing questions of interest not only to legal scholars, but to anyone keen to explore the legal and philosophical foundations of the state. How can a government be legally limited if law is the creation of government? Does this mean that a government can be "self-limiting," or is there some way of avoiding this implication? If meaningful limitation is to be possible, must constitutional constraints be somehow "entrenched"? Must they be enshrined in written rules? If so, how are they to be interpreted? In terms of literal meaning or the intentions of their authors, or in terms of the, possibly ever-changing, values they express? How one answers these questions depends crucially on how one conceives the nature, identity and authority of constitutions. Does a constitution establish a stable framework for the exercise of public power which is in some way fixed by factors like the original meaning or intentions? Or is it a "living tree" which grows and develops in tandem with changing political values and principles?