Abstract
The most important contribution to comparative law in Montesquieu’s Esprit des Lois was the development of a quasi-sociological approach. He focused on extralegal factors to account for differences between legal orders. For contemporary readers, the most surprising among these factors is the climate. In reality, such a climate theory originated in antiquity and can be traced into the 19th century, to some extent beyond. The article traces the history of this idea until our time and discusses both why it was attractive and why it disappeared. It then demonstrates that a revival of some of Montesquieu’s ideas, a new Esprit des Lois de la Nature, is desirable to deal with the current climate crisis. A comparative law in this spirit will require understanding law in its naturecultural context, will need to expand its interdisciplinarity towards the natural sciences, and must pay attention to planetary law.