In this chapter and the next I focus on the arguments and insights of the two most well-known, important, and intellectually sophisticated recent defenders of libertarian or libertarian­leaning doctrines, Robert Nozick (1938­2002) and F. A. Hayek (1899-1992). In this chapter, I begin with Nozick’s Anarchy, State, and Utopia (Nozick 1974) — hereafter, ASU — the work that introduced slumbering academic philosophy to political libertarianism. Nozick offers a moral defense of libertarianism based upon his affirmation of Lockean natural rights to life, liberty, and property. I then turn to the quite different sort of argument for individual liberty and liberty-protective principles of justice that Hayek offers in his The Constitution of Liberty (Hayek 1960) — hereafter, CL — and especially in Rules and Order and The Mirage of Social Justice (Hayek 1973, 1976)- hereafter RO and MSJ respectively — which are the first two volumes of his Law, Legislation, and Liberty. As we shall see, rather than first defending some fundamental and liberty-friendly moral principle from which further libertarian conclusions are to be derived, Hayek begins by correcting what he takes to be deep errors in our understanding of social order and law. Hayek thinks that crucial mistakes about the character and bases for social order and law have dethroned individual liberty and liberty-protective principles of justice. These values will, however, be reinstated when we understand their essential role in a free, flourishing, and pluralistic social and legal order. In the next chapter, I will turn to the implications concerning the nature of and bases for economic justice and property rights that Nozick and Hayek draw from their foundational claims. (Further groundings for libertarian principles and views about economic justice and property rights are discussed in some detail in this book’s bonus online chapter, «Further Philosophical Roads to Libertarianism.”)