One of the critical stages often reached in the evolution of a political movement is the onslaught of infighting. After a common rival is defeated, the ideological victors tend to turn their sights inward, developing their own philosophy systematically by coming to terms with its animating principles. The resulting internecine conflicts are the mark of a movement that has achieved a certain measure of success.

Classical liberalism, according to the scholar George H. Smith, did not begin to take shape as a coherent political theory until the 17th century. In his new book from the Cato Institute and the Cambridge University Press, The System of Liberty, Smith covers some of the themes that run throughout the history of liberalism since that time, highlighting in particular those controversies that divided liberals into different camps.

Smith begins his book with the “defining characteristic of classical liberalism,” which is the value placed on individual freedom. The true liberal treats liberty not simply as a means, he notes, but also as an end in and of itself. In the words of historian Lord Acton, a liberal is a person “whose polar star is liberty — who deems those things right in politics which, taken all round, promote, increase, perpetuate freedom, and those things wrong which impede it.” This focus on freedom, according to Smith, was formulated over time — ultimately culminating in the belief that individuals have “the natural right to use their bodies, labor, and justly acquired property as they see fit, so long as they respect the equal freedom of others.”

This notion was revolutionary. “Just as the authority of religious institutions had previously been undermined by Protestant Reformers,” Smith writes, “so the authority of political institutions now faced a serious challenge from liberal individualists.” The emphasis on liberty was a radical position, one that undercut the widespread belief that government was necessary — indeed, divinely mandated — for maintaining social order.

But classical liberalism was not monolithic, and several important debates arose within the movement over the foundation and proper application of liberal principles. Smith details the emergence of these splits with characteristic insight. Consider two of the debates in particular. The first, that between Benthamite utilitarianism and an older school of natural-rights liberalism, had profound implications for the future of liberalism. Natural-rights theory was the revolutionary doctrine of the seventeenth and eighteenth centuries, Smith argues, being used to justify both resistance to unjust laws and revolution against tyrannical governments. However, “a case can be made,” he continues, “that the triumph of Benthamism, having reduced the value of freedom to calculations of social utility, ripped the moral heart from liberalism and thereby ensured its demise within decades.”

The second conflict centers around the debate between those liberals who advocated a role for the state in education and the “voluntaryists” who called for a complete separation of the two. The relation between school and state has a checkered past in American liberal thought, which Smith details in full. “Only rarely has the voluntaryist wing of liberalism received attention from historians,” he continues, “despite the fact that it was for decades a vibrant movement whose proponents called upon an older form of Lockean liberalism to support their arguments.”

Despite the many challenges throughout the history of classical liberalism, it has experienced a remarkable revival in recent decades. Smith concludes that this is due in part to its ideological predecessors and their efforts to explain and justify individual freedom. In their search for answers to difficult questions, the classical liberals may not have been successful in every respect. But they did have many successes — both theoretical and practical — and, Smith writes, “we owe them an incalculable debt for many of the freedoms we enjoy today.”