Political communities typically organise themselves by an appeal to values. Sometimes the values invoked are abstract ideas such as justice or equality. One such idea is that of law. In many important instances, practices cannot be understood except by reference to the values to which they make an implicit appeal but from which they fall short; and, equally, values cannot be understood except by reference to the practices within which they are imperfectly articulated. This general structure is captured by one strand of Platonic and Aristotelian thought, and is exhibited by the character of philosophy itself. Governance by law establishes a form of human association that is characterised by an orientation towards an idealisation of its own nature. Consequently, jurisprudential reflection upon the nature of law is a necessary and fundamental feature of communities that aspire to governance by law. Keywords: Law, practice, value, association, philosophy, Plato, the state, friendship.