Here is Hazlitt's major philosophical work, in which he grounds a policy of private property and free markets in an ethic of classical utilitarianism, understood in the way Mises understood that term. In writing this book, Hazlitt is reviving an 18th and 19th century tradition in which economists wrote not only about strictly economic issues but also on the relationship between economics and the good of society in general. Adam Smith wrote a moral treatise because he knew that many objections to markets are rooted in these concerns. Hazlitt takes up the cause too, and with spectacular results.
Hazlitt favors an ethic that seeks the long run general happiness and flourishing of all. Action, institutions, rules, principles, customs, ideals, and all the rest stand or fall according to the test of whether they permit people to live together peaceably to their mutual advantage. Critical here is an understanding of the core classical liberal claim that the interests of the individual and that of society in general are not antagonistic but wholly compatible and co-determinous.
In pushing for "rules-utilitarianism," Hazlitt is aware that he is adopting an ethic that is largely rejected in our time, even by the bulk of the liberal tradition. But he makes the strongest case possible, and you will certainly be challenged at every turn.
In addition, the writing style here is unequaled. It was written in 1964 after a lifetime of writing and thinking. He poured an enormous amount of effort into it, with the goal of completing and vindicating Mises's view of ethics, one which had not been taken up by any Misesians apart from Leland Yeager. Indeed, Yeager writes the foreword.
It is not necessary that you finally agree with Hazlitt's view to appreciate his defense of freedom and the market economy, which explains in great detail how the voluntary society benefits all its members, and how the market economy deserves to be regarded as a critical component of a flourishing civilization. His attacks on logical positivism, socialism, aestheticism, and egalitarianism are dazzling. This book will inspire, provoke, and educate.
Hazlitt personally regarded it as his most important lifetime contribution.