For 2000 years, the study of law has assumed that our biological nature is a mere accessory of reason. Stig Jorgensen turns this scientific rationalism on its head. By using biology as his starting point, he portrays reason as a tool of our genes, alongside other survival tools such as our senses and drives. His perspective makes other recent developments in the philosophy of law seem less strange, particularly in the fields of instrumental language philosophy and teleological concept theory. Such hermeneutic approaches have become indispensable to both interpretation theory and the study of law. Those interested in jurisprudence and the philosophy of law will find much to ponder in this thoughtful and lucid book.