Contrary to what may be suggested by traditional historiography, the modern labour contract did not appear through spontaneous generation with the Industrial Revolution. To the contrary, premodern legal forms going back to the feudal era lasted throughout the nineteen century and even later, entirely subjecting groups of workers to the employers' absolutism. The path leading to a rationalization of the legal technique embodied in the modern labour contract was indeed highly complex. Philip Lotmar's colossal study on Der Arbeitsvertrag [The Labour Contract] (published in two parts, 1902 and 1908) illustrates that complexity in an exemplary fashion, especially as regards the social facts of law. From a Law and Society viewpoint, this work remains without doubts worth reading today, in particular when one also takes into consideration the comprehensive review of this treatise made by Max Weber in 1902 and later comments by Hugo Sinzheimer, the founder of the European science of labour law and himself a distinguished legal sociologist. In the following study, the author insists upon the relevance of Weber's and Sinzheimer's critiques of Lotmar as regards the relationship of law to economics, the importance of legal pluralism for a proper understanding of labour law, as well as the interaction between jurisprudence and the sociology of law.