Who defines the public interest? As the contributors to the collection have shown, the question itself is complex: which public and whose interests? The answer is controversial as well: it is not simply politicians and bureaucrats although they have a prominent role. Journalists and academics, community leaders and private citizens have all seized the initiative and asserted their entitlement as members of the public to assert shared interests and common aspirations principally in advocacy but sometimes through action. Does the authority to define the public interest come with a duty to see it promoted and protected? In addition to canvassing competing visions and contrasting expressions of the public interest and their relationship to the common good, the contributors also examine the limits of public interest claims and how a range of professional groups might discharge their obligation to act in the public interest.