Among the issues discussed in the book are the dichotomy of its traditional and modern forms and the respective benefits and disadvantages of inductive and deductive approaches to its ascertainment. In the course of this analysis, the author draws insights from Friedrich August Hayek's theory of law as a 'spontaneous order', an information-processing device which enables the participants of a legal system to make use of decentralised knowledge. The book argues that the major advantage of custom as a source of international law lies in the fact that it is the result of a gradual process of trial and error, rather than the product of deliberate planning. This makes it a particularly apposite source of law in a time of seismic shifts in the distribution of power within a vastly diverse community of States, when a new global order is expected to emerge, the contours of which are not yet clearly discernible.