There are three pillars of jurisprudence: moral theorizing (reflected in natural law, but not exclusive to it); analytic theorizing (reflected in positivism); and sociolegal theorizing (reflected in legal realism). Legal realism exemplifies this third approach to international law theory beyond natural law and positive law covered in Chapters 2 and 3, and it provides a foundation for many theoretical approaches in the chapters that follow. For legal realists, jurisprudence should be conceived not just in terms of what law “is” or “ought” to be, but also in terms of how law obtains meaning, operates, and changes through practice.

In the United States (US), legal realism grew out of and continues to have parallels with European sociolegal thought (sometimes referred to as European legal realism), as well as sociolegal thought around the world. It built from sociological jurisprudence that developed in Europe and the United States in the early twentieth century.