OVER the past few years, an important legal debate has been raging, the full effects of which many lawyers have not yet felt. I am referring to the taxonomy debate and, specifically, the attempts by the late Professor Peter Birks and (the mainly academic) supporters and advocates of his and similar views to impose a coherent and logical taxonomy upon private (common) law. Much more attention should be paid to sound taxonomy, it is argued. This “great project” has been little noticed outside the backwater of the law in which it began, namely the law of restitution (or “unjust enrichment” as the theorists here under consideration would prefer).