This book presents the papers and comments on those papers delivered at a colloquium held at the Australian National University in December 2008 to celebrate 50 years since the publication in the Harvard Law Review of the famous and wide-ranging debate between HLA Hart and Lon L Fuller. These essays do not to re-run that debate and they are not confined to discussion of the jurisprudential issues canvassed by Hart and Fuller. Rather they pick up on strands in the debate and re-think them in the light of social, political and intellectual developments in the past 50 years and changed ways of understanding law and other normative systems. This collection looks forward rather than backward using the debate as a point of departure and inspiration.