The growing impact of human rights norms on private law has sparked controversy over whether this is a desirable development and, if it is, should take the form of direct or indirect horizontal application of such norms. This paper examines the philosophical foundations of indirect horizontal application, exploring both why the horizontal application of such rights should respect rather than displace private law and why private law should nevertheless conform to constitutional human rights. It therefore investigates whether the maintenance of private law as a distinctive legal domain serves a valuable purpose, as well as whether recourse to constitutional human rights contributes to the achievement of that purpose. In doing so, the paper offers critical analyses of libertarian and Rawlsian accounts of private law, drawing on recent developments in Scotland and South Africa, and paying particular attention to an argument put forward by Arthur Ripstein. The paper concludes that a Hegelian account of law offers a better basis for understanding the specific value of private law than a Kantian one. It argues that in constituting the domain of civil society, private law’s pursuit of interpersonal justice makes a distinctive and irreplaceable contribution to the promotion of freedom. Private law nevertheless benefits from recourse to constitutional human rights: In a world of moral diversity, the realm of values established by charters of such rights gives concrete yet elastic shape to a conception of the common good to which private-law reasoning can orientate itself when playing its discrete role in the ‘system of public right’.