Two phenomena — one longstanding but largely hidden, and one contemporary and highly visible — have inspired the topic of this book. First, there is the development of international law through judicial decisions, which runs against the classic view of international law being made by states alone. Second, there is the dramatic increase in the number of international courts, tribunals, and quasi-judicial bodies, with fifty such bodies now in existence, most of which have been established in recent decades. When viewed together, these two phenomena raise the question whether the coherent development of international law is threatened by this multiplicity of international courts.