Watch this lecture from 22:30 to the end. In this lecture, Sandel discusses the concept of social contracts, social compacts, and mutual agreements in civil society. He compares these to the kinds of agreements that are the hallmark of justice for Rawls and the foundation of civil society for Locke and Hobbes. Just laws, or laws that are in accordance with justice, come from these kinds of agreements. For Kant, contracts that generate justice are "ideas of reason." This allows Kant to provide an objective basis for contracts and laws, which is a way to describe laws as over and above subjective preferences.