How can rights be authoritative? How can our individual and social choices be “constrained” by rights? How can we be motivated by such moral considerations? What rights do we have? How may we justify claims to rights? These questions have, at best, only a superficial clarity. More fundamental matters need to be understood in order to crystallize the puzzlements that they express. To clarify questions such as these we turn to a number of theories in moral philosophy. The first of these theories is Plato's (c.427–c.347BCE), and we will be able to find this first approach by outlining the relevant parts of the position he expresses in The Republic. Here we will seek an understanding of two particular matters: first, the way in which we might understand a moral ideal to be independent of human beings and so apparently capable of “constraining” their choices; secondly, the way in which apparently separate issues of reason, reality, knowledge and morality articulate with each other.

The Republic is written in the form of a dialogue, in which the main character is Plato's own teacher, Socrates. The book begins with Socrates describing his return walk to Athens from its seaport, the Piraeus. Chasing after him comes a slave boy with orders to Socrates to wait for his master, Polemarchus. On catching up, Polemarchus points out the superior number of his own companions and pretends to threaten Socrates with force unless Socrates returns with them to the Piraeus.