This book explores the very roots of liberty by examining the development of modern constitutionalism from its ancient and medieval origins. Derived from a series of lectures delivered by Charles Howard McIlwain at Cornell University in the 1938-39 academic year, these lectures provide a useful introduction to the development of modern constitutional forms. McIlwain explores what he calls "the two fundamental correlative elements of constitutionalism for which all lovers of liberty must yet fight" -- "the legal limits to arbitrary power and a complete political responsibility of government to the governed". Despotic power has risen to challenge constitutional governments in many countries, and within this text, McIlwain shows how constitutional safeguards that have been set against government by force have grown in the Western world. McIlwain also outlines the general principles of constitutionalism, especially as an Anglo-American tradition, and traces its development from the law and custom of the Roman Republic through the English common law to the establishment of Americas constitutional government. In Chapter I McIlwain writes, "For perhaps never in its long history has the principle of constitutionalism been so questioned as it is questioned today, never has the attack upon it been so determined or so threatening as it is just now. The world is trembling in the balance between the orderly procedure of law and the processes of force which seem so much more quick and effective... Whether in the end we decide for law or for force, ...we should retrace the history of our constitutionalism". In tracing the rise of constitutionalism from the ancient Greeks through the modern era, this brief volume on the history of constitutionalism in Western political thought is arguably the leading study of the legal limitations on the power of government.