Eugen Ehrlich (1862–1922) became a founding father of sociology of law. At the core of his work was the attempt to equip jurisprudence with empirical methods hitherto not employed by lawyers: methods adding to the analysis of legal codes and authoritative court rulings. According to Ehrlich, the sociology of law makes the parent subject a legal science. Beyond the meta orientation that is sociological jurisprudence, Ehrlich mentions a range of research techniques, “methods” in the sense of “how do we go about researching law empirically”. Ehrlich highlights analysing legal documents and especially forms of empirical observation. He also briefly mentions experimental methods. This paper discusses research investigating the connection between law and emotions through quasi-experimental designs, the use of Ehrlich’s concepts in historical sociological analysis, the value of comparative empirical research as well as content analysis and observation in contemporary works. “Method is as infinite as science itself” reads the last sentence of Ehrlich’s “Fundamental Principles of the Sociology of Law” and sociologists of law have proven him right.