A cursory examination of the pages of this volume reveals that fully a
quarter of them deal with cases in which the Court has been asked to
protect private interests of one kind or another against legislation,
most generally state legislation, which is alleged to invade "liberty"
or "property" contrary to "due process of law". How is this vast
proliferation of cases, and attendant expansion of the Court's
constitutional jurisdiction, to be explained? The explanation, in brief,
is to be found in the replacement of the original meaning of the due
process clause with a meaning of vastly greater scope. Judicial review
is always a function, so to speak, of the viable Constitutional Law of a
particular period.

From what has been previously said in this Introduction, it clearly
appears that the Court's interpretation of the Constitution has involved
throughout considerable lawmaking, but in no other instance has its
lawmaking been more evident than in its interpretation of the due
process clauses, and in no other instance have the state judiciaries
contributed so much to the final result. The modern concept of
substantive due process is not the achievement of any one American high
court; it is the joint achievement of several--in the end, of all.[58]

The thing which renders the due process clause an important datum of
American Constitutional Law is the role it has played first and last in
articulating certain theories of private immunity with the
Constitutional Document. The first such theory was Locke's conception of
the property right as anterior to government and hence as setting a
moral limit to its powers.[59] But while Locke's influence is seen to
pervade the Declarations and Bills of Rights which often accompanied the
revolutionary State Constitutions, yet their promise was early defeated