Books on American constitutional law should be simple, comprehensive, authoritative, and specially adapted to the conditions under which the subject is pursued. In later years the subject is usually approached through two books: a treatise on constitutional law, and a book (collection) of leading cases illustrative of the principles involved. The tendency is toward bulky volumes. Meanwhile other subjects than constitutional law,—other branches of the law,—must be pursued. Multiplicity of subjects is characteristic of the curriculum whether at Law School or at College or University. Time is brief: studies are many. The necessary result is concentration upon the essentials of a subject,—careful isolation of its principles together with familiarity with authoritative illustrations of their application. This means a small, compact, authoritative book on the subject. There are few principles,—there are innumerable applications of them. Values are twofold,—perception of the principle, and understanding of its application. The question is not “What principle?” but rather, “What application?” Thus the student of law may wisely be led to consider, to weigh, to study the great or the leading application of a principle: that is, he is properly directed to the important decisions of the Courts of Law. In America, these decisions are handed down by the Supreme Courts of States and the Supreme Court of the United States. From these decisions the principles of our constitutional law may be derived. Great writers, like Hamilton, Madison, Kent, Story, or Cooley, must be listened to: but it is the Court of Law that speaks with authority. Our great writers on constitutional law and our great judges sitting as Courts of Law practically agree as to what comprise the principles of our constitutional law. Whether the principles of the law are reached by induction or by deduction does not affect the principles. Judicial decisions illustrate both methods of approach. Stated broadly,—a treatise on constitutional law sets forth its principles and cites decisions as illustrations of their application; a collection of cases provides many illustrations from which the principles may be, or are, deduced. By combining the treatise and the case-book (and the present volume may be used in connection with any of the current “Collections” of “Leading Cases”) the benefits of both methods,—deductive and inductive,—are realized. Whether the two sorts of books are used together, or in succession, must depend upon the time, the place, and the importance assigned to the subject itself. Highly beneficial results have followed when a first semester has been given to the treatise, and a second to the cases, whether in a “Collection” (of which there are several of highest value now in use), or in the original “Reports.”