Like so much else that he wrote, Shakespeare's comments on greatness strike a resonant chord – “In my stars I am above thee; but be not afraid of greatness: some are born great, some achieve greatness, and some have greatness thrust upon ’em.” But he gives us very little hint of what greatness might be. Indeed, it is an elusive quality that defies easy or obvious clarification. Like the setting of Shakespeare's words in Twelfth Night, it is a many-layered concept whose meaning takes on shape and color depending on its context. In the play, although Malvolio says the words, they are in fact contained in a letter that is part of an elaborate ruse by Maria, who composes the letter in Olivia's hand. Similarly, greatness is very much a quality that shifts and reconstitutes itself as circumstances demand. Being great is as much about setting the defining terms as about meeting them.

One of those judges who can lay a relatively uncontroversial claim to greatness is the eighteenth-century Lord Mansfield; he aligned the common law more closely to the pursuit of substantive justice. He was at ground zero of the early efforts to construct the modern foundations of the common law. As long as some allowance is made for the immediate conditions and historical constraints under which he worked, he has been anointed as the very model of a great judge – his claim to greatness has not only withstood the test of time but also been bolstered by it. Consequently, the challenge is not to make the case for Mansfield's inclusion in the ranks of great judges, but to inquire into and identify what made him great. In doing so, we might be able to get a better handle on the qualities of greatness that have motivated most lawyers and others in their assessments of later judges.